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13 pages, 2854 KiB

Open AccessArticle

Synergistic Integration of MXene and Metal-Organic Frameworks for Enhanced Electrocatalytic Hydrogen Evolution in an Alkaline Environment

by Low Ping Hao, Abdul Hanan, Rashmi Walvekar, Mohammad Khalid, Faiza Bibi, Wai Yin Wong and Chander Prakash

Catalysts 2023, 13(5), 802; https://doi.org/10.3390/catal13050802 - 26 Apr 2023

Cited by 36 | Viewed by 2752

Abstract

The development of transition metal (TM) catalysts to replace precious metals has garnered increasing interest. Specifically, platinum (Pt)-based catalysts have been extensively investigated for their electrochemical performance in hydrogen evolution reaction (HER), which offer a clean means of producing hydrogen fuel without carbon [...] Read more.

The development of transition metal (TM) catalysts to replace precious metals has garnered increasing interest. Specifically, platinum (Pt)-based catalysts have been extensively investigated for their electrochemical performance in hydrogen evolution reaction (HER), which offer a clean means of producing hydrogen fuel without carbon emissions. However, the reliance on Pt-based catalysts has hindered the progress of HER development. Therefore, researchers have explored metal-organic frameworks (MOFs) as a substitute for noble Pt-based catalysts to address this issue. Nevertheless, the low electroconductivity of pure MOFs restricts their application in electrochemical fields. To overcome this limitation, MXenes have emerged as a promising two-dimensional (2D) material for coupling with MOFs to create an electrocatalyst with high electrical conductivity, a large surface area, and a tunable structure. In this study, we report the synthesis of a Ti₃C₂T_x (MXene) nanosheet-encapsulated MOFs catalyst (Ti₃C₂T_x@ZIF-8) with high activity and a low cost by encapsulating the precursor with ZIF-8 for HER in alkaline media. The catalyst exhibits an overpotential of only 507 mV at 20 mA/cm² and a low Tafel slope value of 77 mV/dec. Additionally, cyclic voltammetry (CV) indicates an electrochemical active surface area (ECSA) of 122.5 cm², and chronopotentiometry demonstrates the stable nature of the catalyst over 20 h without any significant changes in the overpotential value. The excellent electrochemical properties of Ti₃C₂T_x@ZIF-8 suggest its potential as a promising material for energy conversion applications. Full article

(This article belongs to the Special Issue Synthesis and Photocatalytic Activity of Composite)

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19 pages, 5685 KiB

Open AccessFeature PaperArticle

Synthesis of Highly Efficient (0D/1D) Z-Scheme CdS-NPs@ZnO-NRs Visible-Light-Driven Photo(electro)catalyst for PEC Oxygen Evolution Reaction and Removal of Tetracycline

by Sridharan Balu, Harikrishnan Venkatesvaran, Kuo-Wei Lan and Thomas C.-K. Yang

Catalysts 2022, 12(12), 1601; https://doi.org/10.3390/catal12121601 - 7 Dec 2022

Cited by 6 | Viewed by 2456

Abstract

Herein, we synthesized the cadmium sulfide nanoparticles (CdS-NPs) coated zinc oxide nanorods (ZnO-NRs) core-shell like CdS-NPs@ZnO-NRs heterojunction for photo(electro)chemical applications. The CdS-NPs and ZnO-NRs were synthesized through a simple hydrothermal path. The physicochemical and optoelectronic properties of the as-prepared catalysts are characterized by [...] Read more.

Herein, we synthesized the cadmium sulfide nanoparticles (CdS-NPs) coated zinc oxide nanorods (ZnO-NRs) core-shell like CdS-NPs@ZnO-NRs heterojunction for photo(electro)chemical applications. The CdS-NPs and ZnO-NRs were synthesized through a simple hydrothermal path. The physicochemical and optoelectronic properties of the as-prepared catalysts are characterized by various spectroscopy techniques, such as FTIR, XRD, SEM, TEM, EDX, VB-XPS, DRS, and PL. The photocatalytic performances of the CdS-NPs@ZnO-NRs catalyst were evaluated by photodegradation of tetracycline (TC) in aqueous media under visible-light irradiation, which demonstrated 94.07 % of removal (k’ = 0.0307 min⁻¹) within 90 min. On the other hand, the photoelectrochemical (PEC) water-oxidation/oxygen-evolution reaction (OER) was performed, which resulted in the photocurrent density of 3.002 mA/cm² and overpotential (at 2 mA/cm²) of 171 mV (vs RHE) in 1.0 M KOH under AM 1.5G illumination. The reactive species scavenging experiment demonstrates the significant contributions of photogenerated holes towards TC removal. Furthermore, the Z-scheme CdS-NPs@ZnO-NRs core-shell heterojunction exhibits high efficiency, recyclability, and photostability, demonstrating that the CdS-NPs@ZnO-NRs is a robust photo(electro)catalyst for visible-light PEC applications. Full article

(This article belongs to the Special Issue Synthesis and Photocatalytic Activity of Composite)

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17 pages, 7619 KiB

Open AccessArticle

Visible-Light-Active Vanadium and Copper Co-Doped gCN Nanosheets with Double Direct Z-Scheme Heterojunctions for Photocatalytic Removal of Monocrotophos Pesticide in Water

by Dhanapal Vasu, Arjunan Karthi Keyan, Subramanian Sakthinathan, Chung-Lun Yu, Yu-Feng You, Te-Wei Chiu, Liangdong Fan and Po-Chou Chen

Catalysts 2022, 12(11), 1489; https://doi.org/10.3390/catal12111489 - 21 Nov 2022

Cited by 7 | Viewed by 2128

Abstract

In this study, both vanadium and copper elements were anchored on graphitic carbon nitride (gCN) (denoted as V/Cu/gCN) via a thermal decomposition process as a novel nanosheet photocatalyst for the removal of monocrotophos (MCP). The prepared nanosheet features were studied by utilizing XRD, [...] Read more.

In this study, both vanadium and copper elements were anchored on graphitic carbon nitride (gCN) (denoted as V/Cu/gCN) via a thermal decomposition process as a novel nanosheet photocatalyst for the removal of monocrotophos (MCP). The prepared nanosheet features were studied by utilizing XRD, UV–Visible absorption spectrometry, PL, FE-SEM, TEM, and XPS techniques. These analytical techniques revealed the successful formation of direct Z-scheme heterojunctions of V/Cu/gCN nanosheets. The dopant materials significantly enhanced the electron–hole separation and enhanced the removal rate of MCP as compared with bulk gCN. The investigation of effective operating conditions confirmed that a higher removal of MCP could be obtained at a doping concentration of 0.3 wt% and a catalytic dosage of 8 mg with 80 min of visible-light irradiation. The generation of various reactive radicals during the degradation process of the photocatalyst was observed using a scavenging treatment process. Additionally, the scavenging process confirmed that e⁻, OH•, h⁺, and O₂^•− played a major role in MCP degradation. The direct Z-scheme dual-heterojunction mechanism, as well as the possible pathway for the fragmentation of MCP by the V/Cu/gCN nanosheet photocatalyst, was derived in detail. This research article provides a novel perspective on the formation of excellent semiconductor photocatalysts, which exhibit enormous potential for environmental treatments. Full article

(This article belongs to the Special Issue Synthesis and Photocatalytic Activity of Composite)

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15 pages, 11405 KiB

Open AccessArticle

Novel Indium Vanadium Oxide Nanosheet-Supported Nickel Iron Oxide Nanoplate Heterostructure for Synergistically Enhanced Photocatalytic Degradation of Tetracycline

by N. Sreeram, V. Aruna, Ravindranadh Koutavarapu, Dong-Yeon Lee and Jaesool Shim

Catalysts 2022, 12(11), 1471; https://doi.org/10.3390/catal12111471 - 18 Nov 2022

Cited by 9 | Viewed by 2015

Abstract

Semiconductor-based heterogeneous photocatalytic oxidation processes have received considerable attention for the remediation of toxic pollutants. Herein, InVO₄/NiFe₂O₄ nanocomposites were synthesized using a facile hydrothermal technique. Furthermore, various characterization results revealed the successful loading of NiFe₂O₄ [...] Read more.

Semiconductor-based heterogeneous photocatalytic oxidation processes have received considerable attention for the remediation of toxic pollutants. Herein, InVO₄/NiFe₂O₄ nanocomposites were synthesized using a facile hydrothermal technique. Furthermore, various characterization results revealed the successful loading of NiFe₂O₄ nanoplates over InVO₄ nanosheets, thereby signifying the formation of a heterostructure. The performance of the synthesized photocatalyst was tested for tetracycline (TC) antibiotic removal. The optimized InVO₄/NiFe₂O₄ nanocomposite exhibits maximum photodegradation of TC molecules (96.68%) in 96 min; this is approximately 6.47 and 4.93 times higher than that observed when using NiFe₂O₄ and InVO₄, respectively. The strong interaction between the InVO₄ nanosheets and NiFe₂O₄ nanoplates can improve the visible-light absorption and hinder the recombination of charge carriers, further enhancing the photocatalytic performance. Moreover, hydroxyl radicals play a crucial role in the photodegradation of TC antibiotics. Full article

(This article belongs to the Special Issue Synthesis and Photocatalytic Activity of Composite)

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14 pages, 6394 KiB

Open AccessArticle

Natural Polymer-Based Iron Oxide (Fe₃O₄) Synthesis, Characterization and Its Application for 1-Amino-Nitrobenzene Degradation in Assistance with Oxidants

by Jayachandrabal Balachandramohan, Mithun Kumar, Thirugnanasambandam Sivasankar and Manickam Sivakumar

Catalysts 2022, 12(10), 1161; https://doi.org/10.3390/catal12101161 - 2 Oct 2022

Cited by 3 | Viewed by 1625

Abstract

A natural polymer-based iron oxide (Fe₃O₄) nanocomposite was prepared through a sonochemical-assisted precipitation method. Characterization studies such as X-ray diffractometer, scanning electron microscopy, and transmission electron microscopy have revealed that the synthesized nanocomposites are homogenously distributed, having an average [...] Read more.

A natural polymer-based iron oxide (Fe₃O₄) nanocomposite was prepared through a sonochemical-assisted precipitation method. Characterization studies such as X-ray diffractometer, scanning electron microscopy, and transmission electron microscopy have revealed that the synthesized nanocomposites are homogenously distributed, having an average size of ~49 nm with a cubical spinel structure. The toxic 1-amino-nitrobenzene was initially treated with a sonophotochemical process in the presence of synthesized nanocomposites, resulting in lower efficiency, whereas with the addition of oxidants, the efficiency enhanced significantly. The parametric effects with respect to the initial solution pH, nanocomposites dose, 1-amino-nitrobenzene concentration, and oxidant concentration were studied, and it was found that an approximately 75% removal efficiency of 1-amino-nitrobenzene was achieved within 120 min. Further, the performance of the catalyst on the oxidation of 1-amino-nitrobenzene with sodium persulfate was also investigated, and it was found that a 95% removal efficiency was attained. Full article

(This article belongs to the Special Issue Synthesis and Photocatalytic Activity of Composite)

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20 pages, 10017 KiB

Open AccessArticle

Photo–Redox Properties of –SO₃H Functionalized Metal-Free g-C₃N₄ and Its Application in the Photooxidation of Sunset Yellow FCF and Photoreduction of Cr (VI)

by Harikrishnan Venkatesvaran, Sridharan Balu, Anuradha Chowdhury, Shih-Wen Chen and Thomas C.-K. Yang

Catalysts 2022, 12(7), 751; https://doi.org/10.3390/catal12070751 - 7 Jul 2022

Cited by 11 | Viewed by 2725

Abstract

In this work, we synthesized a metal-free sulfonic functionalized graphitic carbon nitride using sulfuric acid through the wet impregnation technique. The functionalization of sulfonic groups (–SO₃H) on g-C₃N₄ will promote a high surface charge density and charge separation [...] Read more.

In this work, we synthesized a metal-free sulfonic functionalized graphitic carbon nitride using sulfuric acid through the wet impregnation technique. The functionalization of sulfonic groups (–SO₃H) on g-C₃N₄ will promote a high surface charge density and charge separation owing to its high electronegativity. The g-C₃N₄–SO₃H shows excellent optical/electronic and surface properties towards enhanced photo–redox reactions. The sulfonic groups also facilitate the availability of more separated charge carriers for photocatalytic oxidation and reduction reactions. The as-synthesized material has been characterized by different spectroscopic tools to confirm the presence of functionalized –SO₃H groups and optoelectronic possessions. The photocatalytic responses of g-C₃N₄–SO₃H result in 99.56% photoreduction of Cr (VI) and 99.61% photooxidation of Sunset Yellow FCF within 16 min and 20 min, respectively, of visible light irradiation. The g-C₃N₄–SO₃H catalyst exhibits a high apparent rate constant (K_app) towards the degradation of Cr (VI), and SSY, i.e., 0.783 min⁻¹ and 0.706 min⁻¹, respectively. The intense optical–electrochemical properties and potentially involved active species have been analyzed through transient photocurrent, electrochemical impedance, and scavenging studies. Consequently, the photocatalytic performances are studied under different reaction parameters, and the plausible photocatalytic mechanism is discussed based on the results. Full article

(This article belongs to the Special Issue Synthesis and Photocatalytic Activity of Composite)

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19 pages, 4325 KiB

Open AccessArticle

Solar-Energy-Driven Cu-ZnO/TiO₂ Nanocomposite Photocatalyst for the Rapid Degradation of Congo Red Azo Dye

by Vividha Kondba Landge, Chao-Ming Huang, Vikas Sadashiv Hakke, Shirish Hari Sonawane, Sivakumar Manickam and Ming-Chun Hsieh

Catalysts 2022, 12(6), 605; https://doi.org/10.3390/catal12060605 - 2 Jun 2022

Cited by 9 | Viewed by 2742

Abstract

This study effectively demonstrates the sonochemical synthesis of visible-light-responsive Cu-ZnO/TiO₂ ternary Z-scheme heterojunction nanocomposite photocatalyst. The as-prepared photocatalyst was comprehensively characterized by techniques including high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FE-SEM) with energy dispersive X-ray analysis (EDX) and [...] Read more.

This study effectively demonstrates the sonochemical synthesis of visible-light-responsive Cu-ZnO/TiO₂ ternary Z-scheme heterojunction nanocomposite photocatalyst. The as-prepared photocatalyst was comprehensively characterized by techniques including high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FE-SEM) with energy dispersive X-ray analysis (EDX) and elemental dot mapping, X-ray diffraction (XRD), UV-Vis-diffuse reflectance spectroscopy (UV-Vis-DRS), Brunauer–Emmett–Teller (BET) surface area, and Fourier-transform infrared spectroscopy (FTIR). The photocatalytic activity of the Cu-ZnO/TiO₂ nanocomposite photocatalyst was assessed for the degradation of Congo red (CR), an azo dye, under direct sunlight. The pseudo-first-order rate constant for CR degradation was found to be 0.09 min⁻¹. The outcome implies that the synthesised nanocomposite photocatalyst demonstrates excellent photocatalytic activity under direct sunlight as 98% degradation of CR dye was achieved in approximately 20 min using the Cu-ZnO/TiO₂ nanocomposite photocatalyst. Furthermore, its high recoverability and reusability of five times indicate its excellent catalytic potential. Full article

(This article belongs to the Special Issue Synthesis and Photocatalytic Activity of Composite)

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13 pages, 3244 KiB

Open AccessArticle

Fabrication of 5 V High-Performance Solid-State Asymmetric Supercapacitor Device Based on MnO₂/Graphene/Ni Electrodes

by Ming-Chun Hsieh, Bo-Han Chen, Zhong-Yun Hong, Jue-Kai Liu, Pin-Cheng Huang and Chao-Ming Huang

Catalysts 2022, 12(5), 572; https://doi.org/10.3390/catal12050572 - 23 May 2022

Cited by 12 | Viewed by 2699

Abstract

To reach high energy density and excellent cycle stability, an asymmetric supercapacitor device combining a high-power electric double-layer capacitor (EDLC) anode and high energy density battery-type cathode has been designed and fabricated. A binder-free strategy was used to prepare cathode by coating graphene [...] Read more.

To reach high energy density and excellent cycle stability, an asymmetric supercapacitor device combining a high-power electric double-layer capacitor (EDLC) anode and high energy density battery-type cathode has been designed and fabricated. A binder-free strategy was used to prepare cathode by coating graphene (G) on Ni foam (Ni), then electrodepositing MnO₂, followed by calcination process. The potentiodynamic (PD) electrodeposition cycles of MnO₂ onto graphene significantly impact the electrochemical properties. Benefiting from the hierarchical structure and binder-free process of the designed 75 C/G/Ni hybrid cathode, potentiostatic (PS) electrodeposition followed by PD electrodeposition for 75 cycles demonstrates a high specific capacitance of 691 F g⁻¹ at 2 A g⁻¹. The enhanced capacitive performance can be attributed to the synergistic effect between MnO₂ nanosheets and graphene, in which graphene can serve as ideal support matrix and conductive channels. Furthermore, an asymmetric supercapacitor was fabricated with 75 C/G/Ni and (G + AC)/Ni as the cathode and anode, respectively, and a carboxymethyl cellulose–potassium hydroxide (CMC-KOH) gel electrolyte. The 75 C/G/Ni//(G + AC)/Ni asymmetric supercapacitor (ASC) exhibits a maximum energy density of 43 kW kg⁻¹ at a power density of 302 W kg⁻¹ with a potential window of 1.6 V and maintains good cycling stability of 88% capacitance retention at 2 A g⁻¹ (over 5000 cycles). Four solid-state asymmetric supercapacitors stack connected in series display an effective 5.0 V working potential to increase the voltage and output energy as a device. The device was charged using a 18,650 Li battery with a voltage of +3.8 V for 30 s and discharged six white LEDs for 20 min. The facile fabrication and remarkable capacitive performance of the MnO₂/G/Ni hybrid make it a promising electrode candidate in electrochemical energy conversion/storage devices. Full article

(This article belongs to the Special Issue Synthesis and Photocatalytic Activity of Composite)

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13 pages, 2444 KiB

Open AccessArticle

Effect of the Heterovalent Doping of TiO₂ with Sc³⁺ and Nb⁵⁺ on the Defect Distribution and Photocatalytic Activity

by Petr D. Murzin, Aida V. Rudakova, Alexei V. Emeline and Detlef W. Bahnemann

Catalysts 2022, 12(5), 484; https://doi.org/10.3390/catal12050484 - 25 Apr 2022

Cited by 7 | Viewed by 2222

Abstract

Two series of Sc³⁺- and Nb⁵⁺-doped TiO₂ (rutile) samples were synthesized and characterized by SEM, ICPE spectroscopy, XPS, and BET methods. Photocatalytic activity of the doped TiO₂ samples was tested in photocatalytic degradation of phenol. Dependences of [...] Read more.

Two series of Sc³⁺- and Nb⁵⁺-doped TiO₂ (rutile) samples were synthesized and characterized by SEM, ICPE spectroscopy, XPS, and BET methods. Photocatalytic activity of the doped TiO₂ samples was tested in photocatalytic degradation of phenol. Dependences of the photocatalytic activities of the doped TiO₂ samples demonstrate a volcano-like behavior, indicating the existence of the optimal dopant concentrations to achieve the highest activity of photocatalysts. Remarkably, the optimal dopant concentrations correspond to the extrema observed in work function dependences on the dopant concentrations, that indicates a significant energy redistribution of the defect states within the bandgap of TiO₂. Such a redistribution of the defect states is also proven by the alterations of the optical and EPR spectra of the intrinsic Ti³⁺ defect states in TiO₂. Based on the analysis of the experimental results, we conclude that both Sc³⁺ and Nb⁵⁺ doping of TiO₂ results in redistribution of the defect states and the optimal dopant concentrations correspond to the defect structures, which are ineffective in charge carrier recombination, that ultimately leads to the higher photocatalytic activity of doped TiO₂. Full article

(This article belongs to the Special Issue Synthesis and Photocatalytic Activity of Composite)

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11 pages, 4359 KiB

Open AccessArticle

Highly Photoactive Titanium Dioxide Supported Platinum Catalyst: Synthesis Using Cleaner Ultrasound Approach

by Shital B. Potdar, Chao-Ming Huang, BVS Praveen, Sivakumar Manickam and Shirish H. Sonawane

Catalysts 2022, 12(1), 78; https://doi.org/10.3390/catal12010078 - 11 Jan 2022

Cited by 10 | Viewed by 3103

Abstract

Catalysts increase reaction rates; however, the surface area to volume ratio of catalysts has a vital role in catalytic activity. The noble metals such as platinum (Pt) and gold (Au) are expensive; despite this, they have proven their existence in catalysis, motivating the [...] Read more.

Catalysts increase reaction rates; however, the surface area to volume ratio of catalysts has a vital role in catalytic activity. The noble metals such as platinum (Pt) and gold (Au) are expensive; despite this, they have proven their existence in catalysis, motivating the synthesis of supported metal catalysts. Metal catalysts need to be highly dispersed onto the support. In this investigation, an ultrasound approach has been attempted to synthesise highly photoactive titanium dioxide (TiO₂) nanoparticles by the hydrolysis of titanium tetraisopropoxide in an acetone/methanol mixture. To enhance its photocatalytic activity, TiO₂ was doped with Pt. The synthesised photocatalyst was characterised by techniques such as particle size analysis (PSA), XRD, FE-SEM, TEM, and EDX. The enhancement in the surface characteristics of Pt-doped TiO₂ compared with bare TiO₂ support was confirmed with Brunauer–Emmett–Teller (BET) analysis. The enhanced surface area and uniformity in particle size distribution at the nanoscale level were due to the effects of ultrasonic irradiation. The obtained results corroborated the size and composition of the synthesised catalysts. The size of the catalysts is in the nanometre range, and good dispersion of Pt catalysts over the TiO₂ support was observed. The UV-Visible spectroscopy analysis was performed to study the optical properties of the synthesised TiO₂ and Pt/TiO₂ photocatalysts. An increase in the absorbance was noted when Pt was added to TiO₂, which is due to the decrease in the band gap energy. Full article

(This article belongs to the Special Issue Synthesis and Photocatalytic Activity of Composite)

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Review

Jump to: Research

24 pages, 5608 KiB

Open AccessReview

Ag₂CO₃-Based Photocatalyst with Enhanced Photocatalytic Activity for Endocrine-Disrupting Chemicals Degradation: A Review

by Hartini Ahmad Rafaie, Nurul Infaza Talalah Ramli, Zuraida Khusaimi, Mohd Arif Mohd Sarjidan, Paweena Dulyaseree and Zul Adlan Mohd Hir

Catalysts 2023, 13(3), 540; https://doi.org/10.3390/catal13030540 - 8 Mar 2023

Cited by 5 | Viewed by 2507

Abstract

Endocrine-disrupting chemicals (EDCs) in the aquatic environment have garnered a lot of attention during the past few years. Due to their toxic behavior, which interferes with endocrine functions in both humans and aquatic species, these types of compounds have been recognized as major [...] Read more.

Endocrine-disrupting chemicals (EDCs) in the aquatic environment have garnered a lot of attention during the past few years. Due to their toxic behavior, which interferes with endocrine functions in both humans and aquatic species, these types of compounds have been recognized as major polluting agents in wastewater effluents. Therefore, the development of efficient and sustainable removal methods for these emerging contaminants is essential. Photocatalytic removal of emerging contaminants using silver carbonate (Ag₂CO₃)-based photocatalyst is a promising process due to the unique characteristics of this catalyst, such as absorption of a larger fraction of the solar spectrum, wide band gap, non-toxicity, and low cost. The photocatalytic performance of Ag₂CO₃ has recently been improved through the doping of elements and optimization variation of operational parameters resulting in decreasing the rate of electron–hole pair recombination and an increase in the semiconductor’s excitation state efficiency, which enables the degradation of contaminants under UV or visible light exposure. This review summarized some of the relevant investigations related to Ag₂CO₃-based photocatalytic materials for EDC removal from water. The inclusion of Ag₂CO₃-based photocatalytic materials in the water recovery procedure suggests that the creation of a cutting-edge protocol is essential for successfully eliminating EDCs from the ecosystem. Full article

(This article belongs to the Special Issue Synthesis and Photocatalytic Activity of Composite)

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37 pages, 4710 KiB

Open AccessFeature PaperReview

Structurally Modified MXenes-Based Catalysts for Application in Hydrogen Evolution Reaction: A Review

by Raja Rafidah Raja Sulaiman, Abdul Hanan, Wai Yin Wong, Rozan Mohamad Yunus, Kee Shyuan Loh, Rashmi Walvekar, Vishal Chaudhary and Mohammad Khalid

Catalysts 2022, 12(12), 1576; https://doi.org/10.3390/catal12121576 - 4 Dec 2022

Cited by 43 | Viewed by 3630

Abstract

Green hydrogen production via electrocatalytic water splitting paves the way for renewable, clean, and sustainable hydrogen (H₂) generation. H₂ gas is produced from the cathodic hydrogen evolution reaction (HER), where the reaction is catalyzed primarily from Pt-based catalysts under both [...] Read more.

Green hydrogen production via electrocatalytic water splitting paves the way for renewable, clean, and sustainable hydrogen (H₂) generation. H₂ gas is produced from the cathodic hydrogen evolution reaction (HER), where the reaction is catalyzed primarily from Pt-based catalysts under both acidic and alkaline environments. Lowering the loading of Pt and the search for alternative active catalysts for HER is still an ongoing challenge. Two-dimensional MXenes are effective supports to stabilize and homogenously distribute HER-active electrocatalysts to boost the HER performance. Factors involved in the effectiveness of MXenes for their role in HER include transition metal types and termination groups. Recently, tailoring the conditions during the synthesis of MXenes has made it possible to tune the morphology of MXenes from multilayers to few layers (delaminated), formation of porous MXenes, and those with unique crumpled and rolled structures. Changing the morphology of MXenes alters the surface area, exposed active sites and accessibility of electrolyte materials/ions to these active sites. This review provides insight into the effects of varying morphology of MXenes towards the electrocatalytic HER activity of the MXene itself and MXene composites/hybrids with HER-active catalysts. Synthesis methods to obtain the different MXene morphologies are also summarized. Full article

(This article belongs to the Special Issue Synthesis and Photocatalytic Activity of Composite)

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38 pages, 8383 KiB

Open AccessFeature PaperReview

Co-Doped, Tri-Doped, and Rare-Earth-Doped g-C₃N₄ for Photocatalytic Applications: State-of-the-Art

by Bao Lee Phoon, Chong Cheen Ong, Kuan-Ching Lee, Guan-Ting Pan, Bey Fen Leo, Siewhui Chong and Kuan-Lun Pan

Catalysts 2022, 12(6), 586; https://doi.org/10.3390/catal12060586 - 27 May 2022

Cited by 16 | Viewed by 4130

Abstract

Rapid industrialization and overpopulation have led to energy shortages and environmental pollution, accelerating research to solve the issues. Currently, metal-free photocatalysts have gained the intensive attention of scientists due to their environmental-friendly nature and ease of preparation. It was noticed that g-C₃ [...] Read more.

Rapid industrialization and overpopulation have led to energy shortages and environmental pollution, accelerating research to solve the issues. Currently, metal-free photocatalysts have gained the intensive attention of scientists due to their environmental-friendly nature and ease of preparation. It was noticed that g-C₃N₄ (GCN) consists of a few outstanding properties that could be used for various applications such as water treatment and clean energy production. Nonetheless, bare GCN contains several drawbacks such as high charge recombination, limited surface area, and low light sensitivity. Several solutions have been applied to overcome GCN limitations. Co-doping, tri-doping, and rare-earth-doping can be effective solutions to modify the GCN structure and improve its performance toward photocatalysis. This review highlights the function of multi-elemental and rare-earth dopants in GCN structure, mechanisms, and performance for photocatalytic applications as well as the advantages of co-doping, tri-doping, and rare-earth-doping of GCN. This review summarizes the different roles of dopants in addressing the limitations of GCN. Therefore, this article critically reviewed how multi-elemental and rare-earth-doping affect GCN properties and enhanced photoactivity for various applications. Full article

(This article belongs to the Special Issue Synthesis and Photocatalytic Activity of Composite)

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