Molecules

2024

Jump to: 2023

9 pages, 3060 KiB

Open AccessArticle

A Facile Alkali-Assisted Synthesis Strategy for Hierarchical Porous Carbon Aerogels for Supercapacitors

by Huimin Yang, Mingfang Zhang, Xinwei Guan, Xiaogang Shang, Lingfeng Zhu, Haimei Xu and Songbo Li

Molecules 2024, 29(22), 5413; https://doi.org/10.3390/molecules29225413 - 16 Nov 2024

Viewed by 485

Abstract

Carbon aerogels synthesized via the polymerization of resorcinol (R) and formaldehyde (F) exhibit remarkable physiochemical properties, such as high thermal stability and excellent electrical conductivity. However, their limited specific surface area and porosity restrict their application potential. Herein, we developed hierarchical porous carbon [...] Read more.

Carbon aerogels synthesized via the polymerization of resorcinol (R) and formaldehyde (F) exhibit remarkable physiochemical properties, such as high thermal stability and excellent electrical conductivity. However, their limited specific surface area and porosity restrict their application potential. Herein, we developed hierarchical porous carbon aerogels using a one-step carbonization and activation method, directly converting the resin into carbon aerogel material by adding KOH as an activating agent. In contrast to conventional carbon aerogels with an irregular block ground structure, our hierarchical porous carbon aerogels exhibit substantially enhanced specific surface area, total pore volume, and surface oxygen content. In addition, this straightforward one-step fabrication approach holds significant promise for energy storage applications. Notably, the hierarchical porous carbon aerogel C1, with a KOH/RF mass ratio of 1, was proven to be the most effective electrode candidates, achieving a specific capacitance of 261.9 F·g⁻¹ at 1 A·g⁻¹ and 208.2 F·g⁻¹ at 20 A·g⁻¹. Moreover, it exhibited an outstanding rate capability of 79.5% and excellent capacity retention of approximately 97.5% after 10,000 cycles (7 A·g⁻¹). This work highlights a promising approach for synthesizing commercial-grade carbon aerogels with hierarchical porosity, enabling high-performance energy storage applications. Full article

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11 pages, 3896 KiB

Open AccessArticle

Ca-Doping Cobalt-Free Double Perovskite Oxide as a Cathode Material for Intermediate-Temperature Solid Oxide Fuel Cell

by Liangmei Xue, Songbo Li, Shengli An, Qiming Guo, Mengxin Li and Ning Li

Molecules 2024, 29(13), 2991; https://doi.org/10.3390/molecules29132991 - 23 Jun 2024

Cited by 1 | Viewed by 1267

Abstract

Mixed oxygen ion and electron-conducting materials are viable cathodes for solid oxide fuel cells due to their excellent oxygen transport kinetics and mixed electrical conductivity, which ensure highly efficient operation at low and medium temperatures. However, iron-based double perovskite oxides usually exhibit poor [...] Read more.

Mixed oxygen ion and electron-conducting materials are viable cathodes for solid oxide fuel cells due to their excellent oxygen transport kinetics and mixed electrical conductivity, which ensure highly efficient operation at low and medium temperatures. However, iron-based double perovskite oxides usually exhibit poor electrocatalytic activity due to low electron and oxygen ion conductivity. In this paper, Ca is doped in PrBaFe₂O_5+δ A-site to improve the electrochemical performance of PrBaFe₂O_5+δ. Results show that replacing Pr with Ca does not change the crystal structure, and the Ca doping effectively increases the adsorbed oxygen content and accelerates the migration and diffusion rate of O²⁻ to the electrolyte|cathode interface. The polarization resistance of the symmetric cell PC_0.15BF|CGO|PC_0.15BF is 0.033 Ω·cm² at 800 °C, which is about 56% lower than that of PBF, confirming the enhancement of the mixed conduction of oxygen ions and electrons. In addition, the anode-supported single cell has a peak power density of 512 mW·cm⁻² at 800 °C. Full article

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3 pages, 157 KiB

Open AccessEditorial

Catalysis in Energy and the Environment: Opportunities and Challenges

by Xiong He, Yuhao Li and Hongda Li

Molecules 2024, 29(9), 1932; https://doi.org/10.3390/molecules29091932 - 24 Apr 2024

Viewed by 1030

Abstract

Energy and the environment are the foundations of modern human society [...] Full article

20 pages, 5725 KiB

Open AccessArticle

One-Step Synthesis of Polyethyleneimine-Grafted Styrene-Maleic Anhydride Copolymer Adsorbents for Effective Adsorption of Anionic Dyes

by Yao Xu, Qinwen Wang, Yuanbo Wang, Falu Hu, Bin Sun, Tingting Gao and Guowei Zhou

Molecules 2024, 29(8), 1887; https://doi.org/10.3390/molecules29081887 - 21 Apr 2024

Cited by 1 | Viewed by 1503

Abstract

Wastewater containing organic dyes has become one of the important challenges in water treatment due to its high salt content and resistance to natural degradation. In this work, a novelty adsorbent, PEI-SMA, was prepared by grafting polyethyleneimine (PEI) onto styrene-maleic anhydride copolymer (SMA) [...] Read more.

Wastewater containing organic dyes has become one of the important challenges in water treatment due to its high salt content and resistance to natural degradation. In this work, a novelty adsorbent, PEI-SMA, was prepared by grafting polyethyleneimine (PEI) onto styrene-maleic anhydride copolymer (SMA) through an amidation reaction. The various factors, such as pH, adsorbent dosage, contact time, dye concentration, and temperature, which may affect the adsorption of PEI-SMA for Reactive Black 5 (RB5), were systematically investigated by static adsorption experiments. The adsorption process of PEI-SMA for RB5 was more consistent with the Langmuir isotherm model and the pseudo-second-order model, suggesting a single-layer chemisorption. PEI-SMA exhibits excellent adsorption performance for RB5 dye, with a maximum adsorption capacity of 1749.19 mg g^–1 at pH = 2. Additionally, PEI-SMA exhibited highly efficient RB5 competitive adsorption against coexisting Cl⁻ and SO₄²⁻ ions and cationic dyes. The adsorption mechanism was explored, and it can be explained as the synergistic effect of electrostatic interaction, hydrogen bonding and π–π interaction. This study demonstrates that PEI-SMA could act as a high performance and promising candidate for the effective adsorption of anionic dyes from aqueous solutions. Full article

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23 pages, 1807 KiB

Open AccessReview

Research Progress and Application Prospects of Solid-State Hydrogen Storage Technology

by Yaohui Xu, Yang Zhou, Yuting Li and Zhao Ding

Molecules 2024, 29(8), 1767; https://doi.org/10.3390/molecules29081767 - 12 Apr 2024

Cited by 19 | Viewed by 4941

Abstract

Solid-state hydrogen storage technology has emerged as a disruptive solution to the “last mile” challenge in large-scale hydrogen energy applications, garnering significant global research attention. This paper systematically reviews the Chinese research progress in solid-state hydrogen storage material systems, thermodynamic mechanisms, and system [...] Read more.

Solid-state hydrogen storage technology has emerged as a disruptive solution to the “last mile” challenge in large-scale hydrogen energy applications, garnering significant global research attention. This paper systematically reviews the Chinese research progress in solid-state hydrogen storage material systems, thermodynamic mechanisms, and system integration. It also quantitatively assesses the market potential of solid-state hydrogen storage across four major application scenarios: on-board hydrogen storage, hydrogen refueling stations, backup power supplies, and power grid peak shaving. Furthermore, it analyzes the bottlenecks and challenges in industrialization related to key materials, testing standards, and innovation platforms. While acknowledging that the cost and performance of solid-state hydrogen storage are not yet fully competitive, the paper highlights its unique advantages of high safety, energy density, and potentially lower costs, showing promise in new energy vehicles and distributed energy fields. Breakthroughs in new hydrogen storage materials like magnesium-based and vanadium-based materials, coupled with improved standards, specifications, and innovation mechanisms, are expected to propel solid-state hydrogen storage into a mainstream technology within 10–15 years, with a market scale exceeding USD 14.3 billion. To accelerate the leapfrog development of China’s solid-state hydrogen storage industry, increased investment in basic research, focused efforts on key core technologies, and streamlining the industry chain from materials to systems are recommended. This includes addressing challenges in passenger vehicles, commercial vehicles, and hydrogen refueling stations, and building a collaborative innovation ecosystem involving government, industry, academia, research, finance, and intermediary entities to support the achievement of carbon peak and neutrality goals and foster a clean, low-carbon, safe, and efficient modern energy system. Full article

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14 pages, 3239 KiB

Open AccessArticle

Preparation of Oily Sludge-Derived Activated Carbon and Its Adsorption Performance for Tetracycline Hydrochloride

by Jie Long, Piwen He, Krzysztof Przystupa, Yudie Wang and Orest Kochan

Molecules 2024, 29(4), 769; https://doi.org/10.3390/molecules29040769 - 7 Feb 2024

Cited by 3 | Viewed by 1322

Abstract

Oily sludge-derived activated carbon was prepared using the potassium hydroxide (KOH) activation method using oily sludge as a raw material, and one-factor experiments determined the best conditions for preparing activated carbon. The activated carbon’s morphological structure and surface chemical properties were analyzed by [...] Read more.

Oily sludge-derived activated carbon was prepared using the potassium hydroxide (KOH) activation method using oily sludge as a raw material, and one-factor experiments determined the best conditions for preparing activated carbon. The activated carbon’s morphological structure and surface chemical properties were analyzed by scanning different characterization tools, and the adsorption behavior of tetracycline hydrochloride was investigated. The results showed that the optimum conditions for preparing oily sludge-derived activated carbon were an activation temperature of 400 °C, activation time of 30 min, activator concentration of 1 mol/L, and impregnation ratio of 2 mL/g. After activation, the activated carbon had more pores and a more orderly crystal structure arrangement, the specific surface area was 2.07 times higher than that before activation, and the surface was rich in functional groups such as -HO, -C-O, -C=C, and -C-H, which increased the active sites of activated carbon. Physicochemical effects dominated the adsorption process. It belonged to the spontaneous heat absorption process under the quasi-secondary kinetic and Langmuir isothermal models. The maximum monolayer adsorption capacity of KOH-activated carbon was 205.1 mg·g⁻¹. Full article

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13 pages, 3975 KiB

Open AccessArticle

Synergistic Effect of Co₃(HPO₄)₂(OH)₂ Cocatalyst and Al₂O₃ Passivation Layer on BiVO₄ Photoanode for Enhanced Photoelectrochemical Water Oxidation

by Zijun Sun, Zhen Li, Jinlin Chen, Yuying Yang, Chunrong Su, Yumin Lv, Zhenhong Lu, Xiong He and Yongqing Wang

Molecules 2024, 29(3), 683; https://doi.org/10.3390/molecules29030683 - 1 Feb 2024

Cited by 3 | Viewed by 1141

Abstract

Bismuth vanadate (BVO) is regarded as an exceptional photoanode material for photoelectrochemical (PEC) water splitting, but it is restricted by the severe photocorrosion and slow water oxidation kinetics. Herein, a synergistic strategy combined with a Co₃(HPO₄)₂(OH)₂ [...] Read more.

Bismuth vanadate (BVO) is regarded as an exceptional photoanode material for photoelectrochemical (PEC) water splitting, but it is restricted by the severe photocorrosion and slow water oxidation kinetics. Herein, a synergistic strategy combined with a Co₃(HPO₄)₂(OH)₂ (CoPH) cocatalyst and an Al₂O₃ (ALO) passivation layer was proposed for enhanced PEC performance. The CoPH/ALO/BVO photoanode exhibits an impressive photocurrent density of 4.9 mA cm⁻² at 1.23 V_RHE and an applied bias photon-to-current efficiency (ABPE) of 1.47% at 0.76 V_RHE. This outstanding PEC performance can be ascribed to the suppressed surface charge recombination, facilitated interfacial charge transfer, and accelerated water oxidation kinetics with the introduction of the CoPH cocatalyst and ALO passivation layer. This work provides a novel and synergistic approach to design an efficient and stable photoanode for PEC applications by combining an oxygen evolution cocatalyst and a passivation layer. Full article

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2023

Jump to: 2024

12 pages, 1922 KiB

Open AccessArticle

Improvement in the Chromium(VI)-Diphenylcarbazide Determination Using Cloud Point Microextraction; Speciation of Chromium at Low Levels in Water Samples

by Begoña A. Mouco-Novegil, Manuel Hernández-Córdoba and Ignacio López-García

Molecules 2024, 29(1), 153; https://doi.org/10.3390/molecules29010153 - 26 Dec 2023

Cited by 2 | Viewed by 1718

Abstract

A reliable, rapid, and low-cost procedure for determining very low concentrations of hexavalent chromium (Cr) in water is discussed. The procedure is based in the classical reaction of Cr⁶⁺ with diphenylcarbazide. Once this reaction has taken place, sodium dodecylsulfate is added to [...] Read more.

A reliable, rapid, and low-cost procedure for determining very low concentrations of hexavalent chromium (Cr) in water is discussed. The procedure is based in the classical reaction of Cr⁶⁺ with diphenylcarbazide. Once this reaction has taken place, sodium dodecylsulfate is added to obtain an ion-pair, and Triton X-114 is incorporated. Next, the heating of the mixture allows two phases that can be separated by centrifugation to be obtained in a cloud point microextraction (CPE) process. The coacervate contains all the Cr⁶⁺ originally present in the water sample, so that the measurement by molecular absorption spectrophotometry allows the concentration of the metal to be calculated. No harmful organic solvents are required. The discrimination of hexavalent and trivalent forms is achieved by including an oxidation stage with Ce⁴⁺. To take full advantage of the pre-concentration effect inherent to the coacervation process, as well as to minimize reagent consumption and waste generation, a portable mini-spectrophotometer which is compatible with microvolumes of liquid samples is used. The preconcentration factor is 415 and a chromium concentration as low as 0.02 µg L⁻¹ can be detected. The procedure shows a good reproducibility (relative standard deviation close to 3%). Full article

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10 pages, 3044 KiB

Open AccessArticle

Core–Shell Structure Trimetallic Sulfide@N-Doped Carbon Composites as Anodes for Enhanced Lithium-Ion Storage Performance

by Xiuyan Li, Liangxing Zhu, Chenyu Yang, Yinan Wang, Shaonan Gu and Guowei Zhou

Molecules 2023, 28(22), 7580; https://doi.org/10.3390/molecules28227580 - 14 Nov 2023

Cited by 3 | Viewed by 1106

Abstract

The high specific capacity of transition metal sulfides (TMSs) opens up a promising new development direction for lithium-ion batteries with high energy storage. However, the poor conductivity and serious volume expansion during charge and discharge hinder their further development. In this work, trimetallic [...] Read more.

The high specific capacity of transition metal sulfides (TMSs) opens up a promising new development direction for lithium-ion batteries with high energy storage. However, the poor conductivity and serious volume expansion during charge and discharge hinder their further development. In this work, trimetallic sulfide Zn–Co–Fe–S@nitrogen-doped carbon (Zn–Co–Fe–S@N–C) polyhedron composite with a core–shell structure is synthesized through a simple self-template method using ZnCoFe–ZIF as precursor, followed by a dopamine surface polymerization process and sulfidation during high-temperature calcination. The obvious space between the internal core and the external shell of the Zn–Co–Fe–S@N–C composites can effectively alleviate the volume expansion and shorten the diffusion path of Li ions during charge and discharge cycles. The nitrogen-doped carbon shell not only significantly improves the electrical conductivity of the material, but also strengthens the structural stability of the material. The synergistic effect between polymetallic sulfides improves the electrochemical reactivity. When used as an anode in lithium-ion batteries (LIBs), the prepared Zn–Co–Fe–S@N–C composite exhibits a high specific capacity retention (966.6 mA h g⁻¹ after 100 cycles at current rate of 100 mA g⁻¹) and good cyclic stability (499.17 mA h g⁻¹ after 120 cycles at current rate of 2000 mA g⁻¹). Full article

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12 pages, 3786 KiB

Open AccessArticle

Significance of Zn Complex Concentration on Microstructure Evolution and Corrosion Behavior of Al/WS₂

by Pratiksha P. Gawas, Praveenkumar Pandurangan, Marzieh Rabiei, Arvydas Palevicius, Andrius Vilkauskas, Giedrius Janusas, Mozhgan Hosseinnezhad, Reza Ebrahimi-Kahrizsangi, Sohrab Nasiri, Jean Michel Nunzi and Venkatramaiah Nutalapati

Molecules 2023, 28(21), 7290; https://doi.org/10.3390/molecules28217290 - 27 Oct 2023

Cited by 2 | Viewed by 1269

Abstract

Corrosion is a harmful processes which by definition is a chemical or electrochemical reaction between a substance (usually a metal) and the environment which leads to a change in the properties of the substance and has destructive effects. In this study, new composites [...] Read more.

Corrosion is a harmful processes which by definition is a chemical or electrochemical reaction between a substance (usually a metal) and the environment which leads to a change in the properties of the substance and has destructive effects. In this study, new composites consisting of Al/WS₂/ZnTerp-2TH with 5 and 10 wt.% ZnTerp-2TH were prepared and the results were fully compared. Al/WS₂ played the role of matrix and ZnTerp-2TH played the role of reinforcement. In other words, as a novelty to prevent the corrosion of Al/WS₂, ZnTerp-2TH is designed and synthesized and showed good results when the corrosion ratio was reduced by the existence of ZnTerp-2TH. Furthermore, the NMR and mass analysis of ZnTerp-2TH were carried out, and the thermal properties, X-ray diffraction, Fourier-transform infrared (FTIR) spectroscopy, morphology, energy-dispersive X-ray spectroscopy (EDX) analysis and corrosion behavior of the composites were also discussed in detail. The crystal size values of composites were calculated by the modified Scherrer method 34, 26 and 27 nm for Al/WS₂, Al/WS₂/5 wt.% ZnTerp-2TH and Al/WS₂/10 wt.% ZnTerp-2TH, respectively. The microstructural examination of the specimens showed that the reinforcing phase (ZnTerp-2TH) has a favorable distribution on the surface of Al/WS₂ when it covers the cracks and holes. In addition, the corrosion investigation results showed that the addition of ZnTerp-2TH to Al/WS₂ can improve the corrosion resistance when the E_corr and I_corr values of Al/WS₂/10 wt.% ZnTerp-2TH were recorded in tandem −724 mV/decade and 5 uA cm⁻². Full article

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15 pages, 3821 KiB

Open AccessArticle

Effectively Controlled Structures of Si-C Composites from Rice Husk for Oxygen Evolution Catalyst

by Changwei Li, Xin Zhao, Min Gao, Fangong Kong and Honglei Chen

Molecules 2023, 28(16), 6117; https://doi.org/10.3390/molecules28166117 - 18 Aug 2023

Cited by 3 | Viewed by 1524

Abstract

This work explores a simple way to regulate the morphology and structure of biomass-based carbon and effectively utilize its internal functional groups as the substrate for the next energy materials. The unique randomly oriented and highly interconnected cordyceps-like 3D structure of rice husk [...] Read more.

This work explores a simple way to regulate the morphology and structure of biomass-based carbon and effectively utilize its internal functional groups as the substrate for the next energy materials. The unique randomly oriented and highly interconnected cordyceps-like 3D structure of rice husk is formed by direct high-temperature carbonization, and the main component is SiC. The well-arranged cordyceps-like structure of SiC demonstrates a remarkable structural/chemical stability and a high rate of electron migration, and further could be used as a stable substrate for metal deposition and find application in the field of electrocatalysis. The oxygen evolution reaction catalyst (SiC-C@Fe₃O₄) prepared by chemical deposition exhibits a low overpotential (260 mV), low Tafel slope (56.93 mV dec⁻¹), high electrochemical active surface area (54.92 mF cm⁻²), and low Rct value (0.15 Ω) at a current density of 10 mA cm⁻² in 1 M KOH electrolyte. The produced natural Si-C composite materials overcome the limitations imposed by the intricate internal structure of silicon-rich biomass. The existence of this stable substrate offers a novel avenue for maximizing the utilization of rice-husk-based carbon, and broadens its application field. At the same time, it also provides a theoretical basis for the use of rice husks in the field of hydrogen production by electrolysis of water, thus promoting their high-value utilization. Full article

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13 pages, 3518 KiB

Open AccessArticle

Facile Electrochemical Synthesis of Bifunctional Needle-like Co-P Nanoarray for Efficient Overall Water Splitting

by Xiong He, Jiayang Cai, Jie Zhou, Qiyi Chen, Qijun Zhong, Jinghua Liu, Zijun Sun, Dezhi Qu and Yudong Li

Molecules 2023, 28(16), 6101; https://doi.org/10.3390/molecules28166101 - 17 Aug 2023

Cited by 3 | Viewed by 1438

Abstract

The development of low-cost and high-performance bifunctional electrocatalysts for overall water splitting is still challenging. Herein, we employed a facile electrodeposition method to prepare bifunctional cobalt phosphide for overall water splitting. The needle-like cobalt phosphide (Co-P-1) nanoarray is uniformly distributed on nickel foam. [...] Read more.

The development of low-cost and high-performance bifunctional electrocatalysts for overall water splitting is still challenging. Herein, we employed a facile electrodeposition method to prepare bifunctional cobalt phosphide for overall water splitting. The needle-like cobalt phosphide (Co-P-1) nanoarray is uniformly distributed on nickel foam. Co-P-1 exhibits excellent electrocatalytic activity for hydrogen evolution reaction (HER, 85 mV at 10 mA/cm², 60 mV/dec) and oxygen evolution reaction (OER, 294 mV at 50 mA/cm², 60 mV/dec). The cell-voltage of 1.60 V is found to achieve the current density of 10 mA/cm² for overall water splitting in the two-electrode system, comparable to that of previously reported Pt/C/NF||RuO₂/NF. The excellent electrocatalytic performance can be attributed to the needle-like structure with more active sites, accelerated charge transfer and evolved bubbles’ release. This work can provide new approach to the development of a bifunctional electrocatalyst for overall water splitting. Full article

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12 pages, 3252 KiB

Open AccessArticle

In Situ Low-Temperature Carbonization Capping of LiFePO₄ with Coke for Enhanced Lithium Battery Performance

by Fei Guo, Xiaoqi Huang, Yudong Li, Shaohui Zhang, Xiong He, Jinghua Liu, Zhiqiang Yu, Feng Li and Baosheng Liu

Molecules 2023, 28(16), 6083; https://doi.org/10.3390/molecules28166083 - 16 Aug 2023

Cited by 2 | Viewed by 2034

Abstract

Lithium batteries incorporating LiFePO₄ (LFP) as the cathode material have gained significant attention in recent research. However, the limited electronic and ionic conductivity of LFP poses challenges to its cycling performance and overall efficiency. In this study, we address these issues by [...] Read more.

Lithium batteries incorporating LiFePO₄ (LFP) as the cathode material have gained significant attention in recent research. However, the limited electronic and ionic conductivity of LFP poses challenges to its cycling performance and overall efficiency. In this study, we address these issues by synthesizing a series of LiFePO₄/carbon (LFP/C) composites through low-temperature carbonization coating of LFP in the presence of Coke as the carbon source. The resulting lithium batteries utilizing LFP/C as the cathode material exhibited impressive discharge specific capacities of 148.35 mA·h/g and 126.74 mA·h/g at 0.1 C and 1 C rates, respectively. Even after 200 cycles of charging and discharging, the capacities remained remarkably high, with values of 93.74% and 97.05% retention, showcasing excellent cycling stability. Notably, the LFP/C composite displayed exceptional rate capability, and capacity retention of 99.27% after cycling at different multiplication rates. These findings underscore the efficacy of in situ low-temperature carbonization capping of LFP with Coke in significantly improving both the cycling stability and rate capability of lithium batteries. Full article

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21 pages, 7481 KiB

Open AccessArticle

Manganese Removal Using Functionalised Thiosalicylate-Based Ionic Liquid: Water Filtration System Application

by Ain Aqilah Basirun, Wan Azlina Wan Ab Karim, Ng Cheah Wei, Jiquan Wu and Cecilia Devi Wilfred

Molecules 2023, 28(15), 5777; https://doi.org/10.3390/molecules28155777 - 31 Jul 2023

Cited by 2 | Viewed by 1416

Abstract

Aiming at the generation of new functionalised thiosalicylate-based ionic liquids, a polymeric hydrogel consisting of 1-hexylimidazole propionitrile thiosalicylate [HIMP][TS], with a solid biomaterial support based on polyvinyl alcohol (PVA)–alginate beads, was produced. This study aimed to develop a treatment method for removing manganese [...] Read more.

Aiming at the generation of new functionalised thiosalicylate-based ionic liquids, a polymeric hydrogel consisting of 1-hexylimidazole propionitrile thiosalicylate [HIMP][TS], with a solid biomaterial support based on polyvinyl alcohol (PVA)–alginate beads, was produced. This study aimed to develop a treatment method for removing manganese (Mn) heavy metal from industrial wastewater, which is known to be toxic and harmful towards the environment and human health. The method utilised an adsorption-based approach with an alginate adsorbent that incorporated a functionalised thiosalicylate-based ionic liquid. The synthesised smooth round beads of PVA–alginate–[HIMP][TS] adsorbent were structurally characterised using Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM). The Mn concentration and removal efficiency were evaluated using atomic absorption spectroscopy (AAS). Three important parameters were evaluated: pH, adsorbent dosage, and contact time. During optimisation using the interactive factor design of experiments through the Box–Behnken model, the results showed that the system achieved a maximum Mn removal efficiency of 98.91% at an initial pH of 7.15, with a contact time of 60 min, using a bead dosage of 38.26 g/L. The beads were also tested in an available water filtration prototype system to illustrate their industrial application, and the performance showed a removal efficiency of 99.14% with 0 NTU total suspended solid (TSS) and 0.13 mg/L turbidity analysis. The recyclability of PVA–alginate–[HIMP][TS] beads using 0.5 M HCl resulted in four cycles with constant 99% Mn removal. The adsorption capacity of Mn was also determined in optimum conditions with 56 mg/g. Therefore, the alginate–thiosalicylate-based ionic liquid system is considered an effective and environmentally friendly method for removing Mn heavy metal due to the high removal efficiency achieved. Full article

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12 pages, 11633 KiB

Open AccessArticle

Ru and Se Co-Doped Cobalt Hydroxide Electrocatalyst for Efficient Hydrogen Evolution Reactions

by Weizhong Peng, Yuting Yuan, Chao Huang, Yulong Wu, Zhaohui Xiao and Guanghui Zhan

Molecules 2023, 28(15), 5736; https://doi.org/10.3390/molecules28155736 - 28 Jul 2023

Cited by 7 | Viewed by 1344

Abstract

The development of efficient electrocatalysts for hydrogen evolution reactions is an extremely important area for the development of green and clean energy. In this work, a precursor material was successfully prepared via electrodeposition of two doping elements to construct a co-doped cobalt hydroxide [...] Read more.

The development of efficient electrocatalysts for hydrogen evolution reactions is an extremely important area for the development of green and clean energy. In this work, a precursor material was successfully prepared via electrodeposition of two doping elements to construct a co-doped cobalt hydroxide electrocatalyst (Ru-Co(OH)₂-Se). This approach was demonstrated to be an effective way to improve the performance of the hydrogen evolution reaction (HER). The experimental results show that the material exhibited a smaller impedance value and a larger electrochemically active surface area. In the HER process, the overpotential was only 109 mV at a current density of 10 mA/cm². In addition, the doping of selenium and ruthenium effectively prevented the corrosion of the catalysts, with the (Ru-Co(OH)₂-Se) material showing no significant reduction in the catalytic performance after 50 h. This synergistic approach through elemental co-doping demonstrated good results in the HER process. Full article

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23 pages, 27379 KiB

Open AccessArticle

The Influence of Oxidation and Nitrogenation on the Physicochemical Properties and Sorption Capacity of Activated Biocarbons Prepared from the Elderberry Inflorescence

by Wiktoria Dąbrowska, Mateusz Gargol, Małgorzata Gil-Kowalczyk and Piotr Nowicki

Molecules 2023, 28(14), 5508; https://doi.org/10.3390/molecules28145508 - 19 Jul 2023

Cited by 3 | Viewed by 1200

Abstract

The main objective of the study was to prepare a series of new activated biocarbons by means of physical and chemical activation of elderberry inflorescence. The influence of carbon matrix nitrogenation/oxidation on the physicochemical properties and sorption abilities of the carbonaceous materials was [...] Read more.

The main objective of the study was to prepare a series of new activated biocarbons by means of physical and chemical activation of elderberry inflorescence. The influence of carbon matrix nitrogenation/oxidation on the physicochemical properties and sorption abilities of the carbonaceous materials was investigated. The impact of initial dye concentration, pH and temperature of the system on methylene blue and rhodamine B removal efficiency was checked. It was shown that activation of elderberry inflorescences with CO₂ or H₃PO₄, and their further modification by introducing nitrogen or oxygen functional groups, allowed us obtain a wide range of materials that differ significantly in terms of the chemical nature of the surface, degree of specific surface development and the type of porous structure generated. The samples prepared by chemical activation proved to be very effective in terms of cationic dyes adsorption. The maximum sorption capacity toward methylene blue and rhodamine B reached the level of 277.8 and 98.1 mg/g, respectively. A better fit to the experimental data was achieved with a Langmuir isotherm than a Freundlich one. It was also shown that the efficiency of methylene blue and rhodamine B adsorption from aqueous solutions decreased with increasing temperature of the system. Full article

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13 pages, 3451 KiB

Open AccessArticle

Electronic Properties and CO₂-Selective Adsorption of (NiB)_n (n = 1~10) Clusters: A Density Functional Theory Study

by Meiling Hou, Xing Zhou, Chao Fu, Tingting Nie and Yu Meng

Molecules 2023, 28(14), 5386; https://doi.org/10.3390/molecules28145386 - 13 Jul 2023

Cited by 2 | Viewed by 1131

Abstract

In this study, we investigated the electronic properties and selective adsorption for CO₂ of nickel boride clusters (NiB)_n, (n = 1~10) using the first principles method. We optimized the structures of the clusters and analyzed their stability based on binding [...] Read more.

In this study, we investigated the electronic properties and selective adsorption for CO₂ of nickel boride clusters (NiB)_n, (n = 1~10) using the first principles method. We optimized the structures of the clusters and analyzed their stability based on binding energy per atom. It was observed that (NiB)_n clusters adopt 3D geometries from n = 4, which were more stable compared to the plane clusters. The vertical electron affinity, vertical ionization energy, chemical potential, and highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap were calculated. Our results revealed that (NiB)₆ and (NiB)₁₀, with high chemical potential, exhibit a higher affinity for CO₂ adsorption due to a charge delivery channel that forms along the Ni→B→CO₂ path. Notably, (NiB)₁₀ demonstrated a more practical CO₂ desorption temperature, as well as a broader window for the selective adsorption of CO₂ over N₂. The density of states analysis showed that the enhanced CO₂ adsorption on (NiB)₁₀ can be attributed to the synergistic effect between Ni and B, which provides more active sites for CO₂ adsorption and promotes the electron transfer from the surface to the CO₂ molecule. Our theoretical results imply that (NiB)₁₀ should be a promising candidate for CO₂ capture. Full article

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14 pages, 3351 KiB

Open AccessArticle

Tunable Resistive Switching Behaviors and Mechanism of the W/ZnO/ITO Memory Cell

by Zhiqiang Yu, Jinhao Jia, Xinru Qu, Qingcheng Wang, Wenbo Kang, Baosheng Liu, Qingquan Xiao, Tinghong Gao and Quan Xie

Molecules 2023, 28(14), 5313; https://doi.org/10.3390/molecules28145313 - 10 Jul 2023

Cited by 4 | Viewed by 1386

Abstract

A facile sol–gel spin coating method has been proposed for the synthesis of spin-coated ZnO nanofilms on ITO substrates. The as-prepared ZnO-nanofilm-based W/ZnO/ITO memory cell showed forming-free and tunable nonvolatile multilevel resistive switching behaviors with a high resistance ratio of about two orders [...] Read more.

A facile sol–gel spin coating method has been proposed for the synthesis of spin-coated ZnO nanofilms on ITO substrates. The as-prepared ZnO-nanofilm-based W/ZnO/ITO memory cell showed forming-free and tunable nonvolatile multilevel resistive switching behaviors with a high resistance ratio of about two orders of magnitude, which can be maintained for over 10³ s and without evident deterioration. The tunable nonvolatile multilevel resistive switching phenomena were achieved by modulating the different set voltages of the W/ZnO/ITO memory cell. In addition, the tunable nonvolatile resistive switching behaviors of the ZnO-nanofilm-based W/ZnO/ITO memory cell can be interpreted by the partial formation and rupture of conductive nanofilaments modified by the oxygen vacancies. This work demonstrates that the ZnO-nanofilm-based W/ZnO/ITO memory cell may be a potential candidate for future high-density, nonvolatile, memory applications. Full article

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14 pages, 2476 KiB

Open AccessArticle

Efficient and Selective Adsorption of Cationic Dye Malachite Green by Kiwi-Peel-Based Biosorbents

by Yanjun Zhao, Xintong Liu, Wenhui Li, Suyun Pei, Yifan Ren, Xinyang Li, Chen Qu, Chuandong Wu and Jiemin Liu

Molecules 2023, 28(14), 5310; https://doi.org/10.3390/molecules28145310 - 10 Jul 2023

Cited by 7 | Viewed by 1728

Abstract

In this study, pristine kiwi peel (KP) and nitric acid modified kiwi peel (NA-KP) based adsorbents were prepared and evaluated for selective removal of cationic dye. The morphology and chemical structure of KP and NA-KP were fully characterized and compared, and results showed [...] Read more.

In this study, pristine kiwi peel (KP) and nitric acid modified kiwi peel (NA-KP) based adsorbents were prepared and evaluated for selective removal of cationic dye. The morphology and chemical structure of KP and NA-KP were fully characterized and compared, and results showed nitric acid modification introduced more functional groups. Moreover, the adsorption kinetics and isotherms of malachite green (MG) by KP and NA-KP were investigated and discussed. The results showed that the adsorption process of MG onto KP followed a pseudo-second-order kinetic model and the Langmuir isotherm model, while the adsorption process of MG onto NA-KP followed a pseudo-first-order kinetic model and the Freundlich isotherm model. Notably, the Langmuir maximum adsorption capacity of NA-KP was 580.61 mg g⁻¹, which was superior to that of KP (297.15 mg g⁻¹). Furthermore, thermodynamic studies demonstrated the feasible, spontaneous, and endothermic nature of the adsorption process of MG by NA-KP. Importantly, NA-KP showed superior selectivity to KP towards cationic dye MG against anionic dye methyl orange (MO). When the molar ratio of MG/MO was 1:1, the separation factor (α_MG/MO) of NA-KP was 698.10, which was 5.93 times of KP. In addition, hydrogen bonding, π-π interactions, and electrostatic interaction played important roles during the MG adsorption process by NA-KP. This work provided a low-cost, eco-friendly, and efficient option for the selective removal of cationic dye from dyeing wastewater. Full article

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12 pages, 2848 KiB

Open AccessArticle

A Novel Dye-Modified Metal–Organic Framework as a Bifunctional Fluorescent Probe for Visual Sensing for Styrene and Temperature

by Jie Yang, Chaojun Ren, Min Liu, Wenwei Li, Daojiang Gao, Hongda Li and Zhanglei Ning

Molecules 2023, 28(13), 4919; https://doi.org/10.3390/molecules28134919 - 22 Jun 2023

Cited by 10 | Viewed by 1551

Abstract

A novel fluorescent probe (C460@Tb-MOFs) was designed and synthesized by encapsulating the fluorescent dye 7-diethylamino-4-methyl coumarin (C460) into a terbium-based metal–organic framework using a simple ultrasonic impregnation method. It is impressive that this dye-modified metal–organic framework can specifically detect styrene and temperature upon [...] Read more.

A novel fluorescent probe (C460@Tb-MOFs) was designed and synthesized by encapsulating the fluorescent dye 7-diethylamino-4-methyl coumarin (C460) into a terbium-based metal–organic framework using a simple ultrasonic impregnation method. It is impressive that this dye-modified metal–organic framework can specifically detect styrene and temperature upon luminescence quenching. The sensing platform of this material exhibits great selectivity, fast response, and good cyclability toward styrene detection. It is worth mentioning that the sensing process undergoes a distinct color change from blue to colorless, providing conditions for the accurate visual detection of styrene liquid and gas. The significant fluorescence quenching mechanism of styrene toward C460@Tb-MOFs is explored in detail. Moreover, the dye-modified metal–organic framework can also achieve temperature sensing from 298 to 498 K with high relative sensitivity at 498 K. The preparation of functionalized MOF composites with fluorescent dyes provides an effective strategy for the construction of sensors for multifunctional applications. Full article

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16 pages, 3786 KiB

Open AccessArticle

Novel Mn⁴⁺-Activated K₂Nb_1−xMo_xF₇ (0 ≤ x ≤ 0.15) Solid Solution Red Phosphors with Superior Moisture Resistance and Good Thermal Stability

by Yuhan Gao, Lei Feng, Linglin Wang, Jun Zheng, Feiyao Ren, Siyu Liu, Zhanglei Ning, Ting Zhou, Xiaochun Wu, Xin Lai and Daojiang Gao

Molecules 2023, 28(11), 4566; https://doi.org/10.3390/molecules28114566 - 5 Jun 2023

Cited by 9 | Viewed by 1680

Abstract

Nowadays, Mn⁴⁺-activated fluoride red phosphors with excellent luminescence properties have triggered tremendous attentions for enhancing the performance of white light-emitting diodes (WLEDs). Nonetheless, the poor moisture resistance of these phosphors impedes their commercialization. Herein, we proposed the dual strategies of “solid [...] Read more.

Nowadays, Mn⁴⁺-activated fluoride red phosphors with excellent luminescence properties have triggered tremendous attentions for enhancing the performance of white light-emitting diodes (WLEDs). Nonetheless, the poor moisture resistance of these phosphors impedes their commercialization. Herein, we proposed the dual strategies of “solid solution design” and “charge compensation” to design K₂Nb_1−xMo_xF₇ novel fluoride solid solution system, and synthesized the Mn⁴⁺-activated K₂Nb_1−xMo_xF₇ (0 ≤ x ≤ 0.15, x represents the mol % of Mo⁶⁺ in the initial solution) red phosphors via co-precipitation method. The doping of Mo⁶⁺ not only significantly improve the moisture resistance of the K₂NbF₇: Mn⁴⁺ phosphor without any passivation and surface coating, but also effectively enhance the luminescence properties and thermal stability. In particular, the obtained K₂Nb_1−xMo_xF₇: Mn⁴⁺ (x = 0.05) phosphor possesses the quantum yield of 47.22% and retains 69.95% of its initial emission intensity at 353 K. Notably, the normalized intensity of the red emission peak (627 nm) for the K₂Nb_1−xMo_xF₇: Mn⁴⁺ (x = 0.05) phosphor is 86.37% of its initial intensity after immersion for 1440 min, prominently higher than that of the K₂NbF₇: Mn⁴⁺ phosphor. Moreover, a high-performance WLED with high CRI of 88 and low CCT of 3979 K is fabricated by combining blue chip (InGaN), yellow phosphor (Y₃Al₅O₁₂: Ce³⁺) and the K₂Nb_1−xMo_xF₇: Mn⁴⁺ (x = 0.05) red phosphor. Our findings convincingly demonstrate that the K₂Nb_1−xMo_xF₇: Mn⁴⁺ phosphors have a good practical application in WLEDs. Full article

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15 pages, 10086 KiB

Open AccessArticle

In Situ Filling of the Oxygen Vacancies with Dual Heteroatoms in Co₃O₄ for Efficient Overall Water Splitting

by Wei Duan, Shixing Han, Zhonghai Fang, Zhaohui Xiao and Shiwei Lin

Molecules 2023, 28(10), 4134; https://doi.org/10.3390/molecules28104134 - 16 May 2023

Cited by 10 | Viewed by 2277

Abstract

Electrocatalytic water splitting is a crucial area in sustainable energy development, and the development of highly efficient bifunctional catalysts that exhibit activity toward both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of paramount importance. Co₃O₄ is a [...] Read more.

Electrocatalytic water splitting is a crucial area in sustainable energy development, and the development of highly efficient bifunctional catalysts that exhibit activity toward both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of paramount importance. Co₃O₄ is a promising candidate catalyst, owing to the variable valence of Co, which can be exploited to enhance the bifunctional catalytic activity of HER and OER through rational adjustments of the electronic structure of Co atoms. In this study, we employed a plasma-etching strategy in combination with an in situ filling of heteroatoms to etch the surface of Co₃O₄, creating abundant oxygen vacancies, while simultaneously filling them with nitrogen and sulfur heteroatoms. The resulting N/S-V_O-Co₃O₄ exhibited favorable bifunctional activity for alkaline electrocatalytic water splitting, with significantly enhanced HER and OER catalytic activity compared to pristine Co₃O₄. In an alkaline overall water-splitting simulated electrolytic cell, N/S-V_O-Co₃O₄ || N/S-V_O-Co₃O₄ showed excellent overall water splitting catalytic activity, comparable to noble metal benchmark catalysts Pt/C || IrO₂, and demonstrated superior long-term catalytic stability. Additionally, the combination of in situ Raman spectroscopy with other ex situ characterizations provided further insight into the reasons behind the enhanced catalyst performance achieved through the in situ incorporation of N and S heteroatoms. This study presents a facile strategy for fabricating highly efficient cobalt-based spinel electrocatalysts incorporated with double heteroatoms for alkaline electrocatalytic monolithic water splitting. Full article

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12 pages, 1284 KiB

Open AccessArticle

A Facile Hydrothermal Synthesis and Resistive Switching Behavior of α-Fe₂O₃ Nanowire Arrays

by Zhiqiang Yu, Jiamin Xu, Baosheng Liu, Zijun Sun, Qingnan Huang, Meilian Ou, Qingcheng Wang, Jinhao Jia, Wenbo Kang, Qingquan Xiao, Tinghong Gao and Quan Xie

Molecules 2023, 28(9), 3835; https://doi.org/10.3390/molecules28093835 - 30 Apr 2023

Cited by 5 | Viewed by 1764

Abstract

A facile hydrothermal process has been developed to synthesize the α-Fe₂O₃ nanowire arrays with a preferential growth orientation along the [110] direction. The W/α-Fe₂O₃/FTO memory device with the nonvolatile resistive switching behavior has been achieved. The [...] Read more.

A facile hydrothermal process has been developed to synthesize the α-Fe₂O₃ nanowire arrays with a preferential growth orientation along the [110] direction. The W/α-Fe₂O₃/FTO memory device with the nonvolatile resistive switching behavior has been achieved. The resistance ratio (R_HRS/R_LRS) of the W/α-Fe₂O₃/FTO memory device exceeds two orders of magnitude, which can be preserved for more than 10³s without obvious decline. Furthermore, the carrier transport properties of the W/α-Fe₂O₃/FTO memory device are dominated by the Ohmic conduction mechanism in the low resistance state and trap-controlled space-charge-limited current conduction mechanism in the high resistance state, respectively. The partial formation and rupture of conducting nanofilaments modified by the intrinsic oxygen vacancies have been suggested to be responsible for the nonvolatile resistive switching behavior of the W/α-Fe₂O₃/FTO memory device. This work suggests that the as-prepared α-Fe₂O₃ nanowire-based W/α-Fe₂O₃/FTO memory device may be a potential candidate for applications in the next-generation nonvolatile memory devices. Full article

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13 pages, 5454 KiB

Open AccessArticle

Monodisperse MoS₂/Graphite Composite Anode Materials for Advanced Lithium Ion Batteries

by Baosheng Liu, Feng Li, Hongda Li, Shaohui Zhang, Jinghua Liu, Xiong He, Zijun Sun, Zhiqiang Yu, Yujin Zhang, Xiaoqi Huang, Fei Guo, Guofu Wang and Xiaobo Jia

Molecules 2023, 28(6), 2775; https://doi.org/10.3390/molecules28062775 - 19 Mar 2023

Cited by 5 | Viewed by 3064

Abstract

Traditional graphite anode material typically shows a low theoretical capacity and easy lithium decomposition. Molybdenum disulfide is one of the promising anode materials for advanced lithium-ion batteries, which possess low cost, unique two-dimensional layered structure, and high theoretical capacity. However, the low reversible [...] Read more.

Traditional graphite anode material typically shows a low theoretical capacity and easy lithium decomposition. Molybdenum disulfide is one of the promising anode materials for advanced lithium-ion batteries, which possess low cost, unique two-dimensional layered structure, and high theoretical capacity. However, the low reversible capacity and the cycling-capacity retention rate induced by its poor conductivity and volume expansion during cycling blocks further application. In this paper, a collaborative control strategy of monodisperse MoS₂/graphite composites was utilized and studied in detail. MoS₂/graphite nanocomposites with different ratios (MoS₂:graphite = 20%:80%, 40%:60%, 60%:40%, and 80%:20%) were prepared by mechanical ball-milling and low-temperature annealing. The graphite sheets were uniformly dispersed between the MoS₂ sheets by the ball-milling process, which effectively reduced the agglomeration of MoS₂ and simultaneously improved the electrical conductivity of the composite. It was found that the capacity of MoS₂/graphite composites kept increasing along with the increasing percentage of MoS₂ and possessed the highest initial discharge capacity (832.70 mAh/g) when MoS₂:graphite = 80%:20%. This facile strategy is easy to implement, is low-cost, and is cosmically produced, which is suitable for the development and manufacture of advance lithium-ion batteries. Full article

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12 pages, 3710 KiB

Open AccessArticle

Fabrication of Noble-Metal-Free Mo₂C/CdIn₂S₄ Heterojunction Composites with Elevated Carrier Separation for Photocatalytic Hydrogen Production

by Hong Qiu, Xiaohui Ma, Hongxia Fan, Yueyan Fan, Yajie Li, Hualei Zhou and Wenjun Li

Molecules 2023, 28(6), 2508; https://doi.org/10.3390/molecules28062508 - 9 Mar 2023

Cited by 6 | Viewed by 1659

Abstract

Molybdenum-based cocatalyst being used to construct heterojunctions for efficient photocatalytic H₂ production is a promising research hotspot. In this work, CdIn₂S₄ was successfully closely supported on bulk Mo₂C via the hydrothermal method. Based on their matching band [...] Read more.

Molybdenum-based cocatalyst being used to construct heterojunctions for efficient photocatalytic H₂ production is a promising research hotspot. In this work, CdIn₂S₄ was successfully closely supported on bulk Mo₂C via the hydrothermal method. Based on their matching band structures, they formed a Type Ⅰ heterojunction after the combination of Mo₂C (1.1 eV, −0.27 V, 0.83 V) and CdIn₂S₄ (2.3 eV, −0.74 V, 1.56 V). A series of characterizations proved that the heterojunction composite had higher charge separation efficiency compared to a single compound. Meanwhile, Mo₂C in heterojunction could act as an active site for hydrogen production. The photocatalytic H₂ production activity of the heterojunction composites was significantly improved, and the maximum activity was up to 1178.32 μmmol h⁻¹ g⁻¹ for 5Mo₂C/CdIn₂S₄ composites. 5Mo₂C/CdIn₂S₄ heterojunction composites possess excellent durability in three cycles (loss of 6%). Additionally, the mechanism of increased activity for composites was also investigated. This study provides a guide to designing noble-metal-free photocatalyst for highly efficient photocatalytic H₂ evolution. Full article

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16 pages, 13789 KiB

Open AccessArticle

Organo-Montmorillonite Modified by Gemini Quaternary Ammonium Surfactants with Different Counterions for Adsorption toward Phenol

by Ran Wei, Yuanhua Mo, Duojiao Fu, Hongqin Liu and Baocai Xu

Molecules 2023, 28(5), 2021; https://doi.org/10.3390/molecules28052021 - 21 Feb 2023

Cited by 4 | Viewed by 1629

Abstract

The discharge of industrial phenol pollutants causes great harm to the natural environment and human health. In this study, phenol removal from water was studied via the adsorption of Na–montmorillonite (Na–Mt) modified by a series of Gemini quaternary ammonium surfactants with different counterions [...] Read more.

The discharge of industrial phenol pollutants causes great harm to the natural environment and human health. In this study, phenol removal from water was studied via the adsorption of Na–montmorillonite (Na–Mt) modified by a series of Gemini quaternary ammonium surfactants with different counterions [(C₁₁H₂₃CONH(CH₂)₂N⁺ (CH₃)₂(CH₂)₂ N⁺(CH₃)₂ (CH₂)₂NHCOC₁₁H₂₃·2Y⁻, Y = CH₃CO₃⁻, C₆H₅COO⁻ and Br⁻, 12–2–12·2Y⁻]. The results of the phenol adsorption indicated that MMt–12–2–12·2Br⁻, MMt–12–2–12·2CH₃CO₃⁻ and MMt–12–2–12·2C₆H₅COO⁻ reached the optimum adsorption capacity, which was 115.110 mg/g, 100.834 mg/g and 99.985 mg/g, respectively, under the conditions of the saturated intercalation concentration at 2.0 times that of the cation exchange capacity (CEC) of the original Na–Mt, 0.04 g of adsorbent and a pH = 10. The adsorption kinetics of all adsorption processes were in good agreement with the pseudo-second-order kinetics model, and the adsorption isotherm was better modeled by Freundlich isotherm. Thermodynamic parameters revealed that the adsorption of phenol was a physical, spontaneous and exothermic process. The results also showed that the counterions of the surfactant had a certain influence on the adsorption performance of MMt for phenol, especially the rigid structure, hydrophobicity, and hydration of the counterions. Full article

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11 pages, 2188 KiB

Open AccessArticle

Study on the Effect of Different Viscosity Reducers on Viscosity Reduction and Emulsification with Daqing Crude Oil

by Fan Zhang, Qun Zhang, Zhaohui Zhou, Lingling Sun and Yawen Zhou

Molecules 2023, 28(3), 1399; https://doi.org/10.3390/molecules28031399 - 1 Feb 2023

Cited by 13 | Viewed by 4078

Abstract

The urgent problem to be solved in heavy oil exploitation is to reduce viscosity and improve fluidity. Emulsification and viscosity reduction technology has been paid more and more attention and its developments applied. This paper studied the viscosity reduction performance of three types [...] Read more.

The urgent problem to be solved in heavy oil exploitation is to reduce viscosity and improve fluidity. Emulsification and viscosity reduction technology has been paid more and more attention and its developments applied. This paper studied the viscosity reduction performance of three types of viscosity reducers and obtained good results. The viscosity reduction rate, interfacial tension, and emulsification performance of three types of viscosity reducers including anionic sulfonate, non-ionic (polyether and amine oxide), and amphoteric betaine were compared with Daqing crude oil. The results showed that the viscosity reduction rate of petroleum sulfonate and betaine was 75–85%. The viscosity reduction rate increased as viscosity reducer concentration increased. An increase in the oil–water ratio and polymer decreased viscosity reduction. When the concentration of erucamide oxide was 0.2%, the ultra-low interfacial tension was 4.41 × 10⁻³ mN/m. When the oil–water ratio was 1:1, the maximum water separation rates of five viscosity reducers were different. With an increase in the oil–water ratio, the emulsion changed from o/w emulsion to w/o emulsion, and the stability was better. Erucamide oxide and erucic betaine had good viscosity reduction and emulsification effects on Daqing crude oil. This work can enrich knowledge of the viscosity reduction of heavy oil systems with low relative viscosity and enrich the application of viscosity reducer varieties. Full article

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