Molecules

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9 pages, 9941 KiB

Open AccessArticle

In Situ Anodic Transition and Cathodic Contamination Affect the Overall Voltage of Alkaline Water Electrolysis

by Zheng Liu, Zhaoyu Liu, Lingxing Zan, Yu Sun, Huizhen Han, Zhe Li, Han Wang, Ting Cao, Yao Zhu, Haiyang Lv, Yuxuan Liu, Juzhe Liu and Xin Bo

Molecules 2024, 29(22), 5298; https://doi.org/10.3390/molecules29225298 - 9 Nov 2024

Viewed by 463

Abstract

NiFe (oxy)hydroxide has been widely used as a benchmark anodic catalyst for oxygen evolution reactions (OERs) in alkaline water electrolysis devices; however, the energy saving actually takes contributions from both the anodic OER and cathodic hydrogen evolution reaction (HER). In this work, we [...] Read more.

NiFe (oxy)hydroxide has been widely used as a benchmark anodic catalyst for oxygen evolution reactions (OERs) in alkaline water electrolysis devices; however, the energy saving actually takes contributions from both the anodic OER and cathodic hydrogen evolution reaction (HER). In this work, we observe the catalytic promotion upon the in situ-derived NiFe (oxy)hydroxide from the NiFe alloy monolithic electrode and also point out that the coupled nickel cathode is contaminated, leading to the loss of HER activity and a reduction in overall efficiency. It is found that Ni²⁺ and Fe³⁺ cations are inevitably detached from the anode into the electrolyte and electrodeposited on the nickel cathode after the three-month industrial simulation. This research presents the significant enhancement of the oxygen evolution catalysis using an in situ aging process and emphasizes that the catalytic application should not only be isolated on the half reaction, but a reasonable coupled electrode match to get rid of the contamination from the electrolyte is also of great significance to sufficiently present the intrinsic catalytic yielding for the real application. Full article

(This article belongs to the Special Issue Advanced Electrode Materials for Electrochemical Energy Storage and Conversion, 2nd Edition)

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13 pages, 7465 KiB

Open AccessArticle

Unveiling the Dynamic Evolution of Catalytic Sites in N-Doped Leaf-like Carbon Frames Embedded with Co Particles for Rechargeable Zn–Air Batteries

by Yuebin Lian, Weilong Xu, Xiaojiao Du, Yannan Zhang, Weibai Bian, Yuan Liu, Jin Xiao, Likun Xiong and Jirong Bai

Molecules 2024, 29(18), 4494; https://doi.org/10.3390/molecules29184494 - 22 Sep 2024

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Abstract

The advancement of cost-effective, high-performance catalysts for both electrochemical oxygen reduction reactions (ORRs) and oxygen evolution reactions (OERs) is crucial for the widespread implementation of metal–air batteries. In this research, we fabricated leaf-like N-doped carbon frames embedded with Co nanoparticles by pyrolyzing a [...] Read more.

The advancement of cost-effective, high-performance catalysts for both electrochemical oxygen reduction reactions (ORRs) and oxygen evolution reactions (OERs) is crucial for the widespread implementation of metal–air batteries. In this research, we fabricated leaf-like N-doped carbon frames embedded with Co nanoparticles by pyrolyzing a ZIF-L/carbon nanofiber (ZIF-L/CNF) composite. Consequently, the optimized ZIF-L/CNF-700 catalyst exhibit exceptional catalytic activities in both ORRs and OERs, comparable to the benchmark 20 wt% Pt/C and RuO₂. Addressing the issue of diminished cycle performance in the Zn–air battery cycle process, further detailed investigations into the post-electrolytic composition reveal that both the carbon framework and Co nanoparticles undergo partial oxidation during both OERs and ORRs. Owing to the varying local pH on the catalyst surface due to the consumption and generation of OH⁻ by OERs and ORRs, after OERs, the product is reduced-size Co particles, while after ORRs, the product is outer-layer Co(OH)₂-enveloping Co particles. Full article

(This article belongs to the Special Issue Advanced Electrode Materials for Electrochemical Energy Storage and Conversion, 2nd Edition)

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17 pages, 2774 KiB

Open AccessArticle

Hydrochar from Pine Needles as a Green Alternative for Catalytic Electrodes in Energy Applications

by Assunta Marrocchi, Elisa Cerza, Suhas Chandrasekaran, Emanuela Sgreccia, Saulius Kaciulis, Luigi Vaccaro, Suanto Syahputra, Florence Vacandio, Philippe Knauth and Maria Luisa Di Vona

Molecules 2024, 29(14), 3286; https://doi.org/10.3390/molecules29143286 - 11 Jul 2024

Viewed by 1038

Abstract

Hydrothermal carbonization (HTC) serves as a sustainable method to transform pine needle waste into nitrogen-doped (N-doped) hydrochars. The primary focus is on evaluating these hydrochars as catalytic electrodes for the oxygen reduction reaction (ORR) and carbon dioxide reduction reaction (CO₂RR), which [...] Read more.

Hydrothermal carbonization (HTC) serves as a sustainable method to transform pine needle waste into nitrogen-doped (N-doped) hydrochars. The primary focus is on evaluating these hydrochars as catalytic electrodes for the oxygen reduction reaction (ORR) and carbon dioxide reduction reaction (CO₂RR), which are pivotal processes with significant environmental implications. Hydrochars were synthesized by varying the parameters such as nitrogen loading, temperature, and residence time. These materials were then thoroughly characterized using diverse analytical techniques, including elemental analysis, density measurements, BET surface area analysis, and spectroscopies like Raman, FTIR, and XPS, along with optical and scanning electron microscopies. The subsequent electrochemical assessment involved preparing electrocatalytic inks by combining hydrochars with an anion exchange ionomer (AEI) to leverage their synergistic effects. To the best of our knowledge, there are no previous reports on catalytic electrodes that simultaneously incorporate both a hydrochar and AEI. Evaluation metrics such as current densities, onset and half-wave potentials, and Koutecky–Levich and Tafel plots provided insights into their electrocatalytic performances. Notably, hydrochars synthesized at 230 °C exhibited an onset potential of 0.92 V vs. RHE, marking the highest reported value for a hydrochar. They also facilitated the exchange of four electrons at 0.26 V vs. RHE in the ORR. Additionally, the CO₂RR yielded valuable C₂ products like acetaldehyde and acetate. These findings highlight the remarkable electrocatalytic activity of the optimized hydrochars, which could be attributed, at least in part, to their optimal porosity. Full article

(This article belongs to the Special Issue Advanced Electrode Materials for Electrochemical Energy Storage and Conversion, 2nd Edition)

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20 pages, 5131 KiB

Open AccessArticle

Thermochemical Activation of Wood with NaOH, KOH and H₃PO₄ for the Synthesis of Nitrogen-Doped Nanoporous Carbon for Oxygen Reduction Reaction

by Galina Dobele, Aleksandrs Volperts, Ance Plavniece, Aivars Zhurinsh, Daina Upskuviene, Aldona Balciunaite, Gediminas Niaura, Luis César Colmenares-Rausseo, Loreta Tamasauskaite-Tamasiunaite and Eugenijus Norkus

Molecules 2024, 29(10), 2238; https://doi.org/10.3390/molecules29102238 - 10 May 2024

Cited by 5 | Viewed by 1307

Abstract

Carbonization of biomass residues followed by activation has great potential to become a safe process for the production of various carbon materials for various applications. Demand for commercial use of biomass-based carbon materials is growing rapidly in advanced technologies, including in the energy [...] Read more.

Carbonization of biomass residues followed by activation has great potential to become a safe process for the production of various carbon materials for various applications. Demand for commercial use of biomass-based carbon materials is growing rapidly in advanced technologies, including in the energy sector, as catalysts, batteries and capacitor electrodes. In this study, carbon materials were synthesized from hardwood using two carbonization methods, followed by activation with H₃PO₄, KOH and NaOH and doping with nitrogen. Their chemical composition, porous structure, thermal stability and structural order of samples were studied. It was shown that, despite the differences, the synthesized carbon materials are active catalysts for oxygen reduction reactions. Among the investigated carbon materials, NaOH-activated samples exhibited the lowest Tafel slope values, of −90.6 and −88.0 mV dec^–1, which are very close to the values of commercial Pt/C at −86.6 mV dec^–1. Full article

(This article belongs to the Special Issue Advanced Electrode Materials for Electrochemical Energy Storage and Conversion, 2nd Edition)

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12 pages, 7495 KiB

Open AccessArticle

Performance Degradation of a Double-Perovskite PrBaCo₂O_5+δ Cathode Operating under a CO₂/H₂O-Containing Atmosphere

by Lin Zhu, Pengzhang Li, Yuanyuan Li, Xiaonan Fu, Yuanyuan Qi, Juntao Wang, Zaixu Liu and Hongyan Yang

Molecules 2024, 29(5), 1063; https://doi.org/10.3390/molecules29051063 - 29 Feb 2024

Cited by 1 | Viewed by 854

Abstract

The electrochemical activity and stability of the PBCO electrode are investigated under the annealing processes in an atmosphere containing CO₂/H₂O for solid oxide fuel cells (SOFCs). The electrochemical impedance spectrum results unequivocally confirm the significant deterioration in PBCO cathode [...] Read more.

The electrochemical activity and stability of the PBCO electrode are investigated under the annealing processes in an atmosphere containing CO₂/H₂O for solid oxide fuel cells (SOFCs). The electrochemical impedance spectrum results unequivocally confirm the significant deterioration in PBCO cathode performance upon annealing under ambient air conditions, particularly when exposed to CO₂/H₂O atmospheres. Microstructure and surface chemical state analyses reveal the segregation of BaO on the PBCO surface, and the formation of insulating BaCO₃ degraded the electrochemical performance. CO₂ and H₂O exhibit a significant induced effect on the segregation of Ba in PBCO to the surfaces, thereby causing a rapid decline in electrode performance. Additionally, the analysis of volume relaxation reveals that the presence of oxygen in the electrode environment can also influence the deposition process occurring on the surface of the electrode. However, this phenomenon is not observed in N₂. This study emphasizes the impact of various gases present in the working atmosphere on surface-separated BaO, which consequently plays a pivotal role in the activity and long-term stability of PBCO electrodes. Full article

(This article belongs to the Special Issue Advanced Electrode Materials for Electrochemical Energy Storage and Conversion, 2nd Edition)

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14 pages, 18276 KiB

Open AccessArticle

Fe₂O₃ Embedded in N-Doped Porous Carbon Derived from Hemin Loaded on Active Carbon for Supercapacitors

by Zitao Yang, Cunhao Luo, Ning Wang, Junshao Liu, Menglong Zhang, Jing Xu and Yongnan Zhao

Molecules 2024, 29(1), 146; https://doi.org/10.3390/molecules29010146 - 26 Dec 2023

Cited by 1 | Viewed by 1162

Abstract

The high power density and long cyclic stability of N-doped carbon make it an attractive material for supercapacitor electrodes. Nevertheless, its low energy density limits its practical application. To solve the above issues, Fe₂O₃ embedded in N-doped porous carbon (Fe [...] Read more.

The high power density and long cyclic stability of N-doped carbon make it an attractive material for supercapacitor electrodes. Nevertheless, its low energy density limits its practical application. To solve the above issues, Fe₂O₃ embedded in N-doped porous carbon (Fe₂O₃/N-PC) was designed by pyrolyzing Hemin/activated carbon (Hemin/AC) composites. A porous structure allows rapid diffusion of electrons and ions during charge–discharge due to its large surface area and conductive channels. The redox reactions of Fe₂O₃ particles and N heteroatoms contribute to pseudocapacitance, which greatly enhances the supercapacitive performance. Fe₂O₃/N-PC showed a superior capacitance of 290.3 F g⁻¹ at 1 A g⁻¹ with 93.1% capacity retention after 10,000 charge–discharge cycles. Eventually, a high energy density of 37.6 Wh kg⁻¹ at a power density of 1.6 kW kg⁻¹ could be delivered with a solid symmetric device. Full article

(This article belongs to the Special Issue Advanced Electrode Materials for Electrochemical Energy Storage and Conversion, 2nd Edition)

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14 pages, 3624 KiB

Open AccessArticle

ZnS/CoS@C Derived from ZIF-8/67 Rhombohedral Dodecahedron Dispersed on Graphene as High-Performance Anode for Sodium-Ion Batteries

by Miao Jia, Wenfeng Chen, Yilin He, Yutong Liu and Mengqiu Jia

Molecules 2023, 28(19), 6914; https://doi.org/10.3390/molecules28196914 - 3 Oct 2023

Cited by 2 | Viewed by 1346

Abstract

Metal sulfides are highly promising anode materials for sodium-ion batteries due to their high theoretical capacity and ease of designing morphology and structure. In this study, a metal–organic framework (ZIF-8/67 dodecahedron) was used as a precursor due to its large specific surface area, [...] Read more.

Metal sulfides are highly promising anode materials for sodium-ion batteries due to their high theoretical capacity and ease of designing morphology and structure. In this study, a metal–organic framework (ZIF-8/67 dodecahedron) was used as a precursor due to its large specific surface area, adjustable pore structure, morphology, composition, and multiple active sites in electrochemical reactions. The ZIF-8/67/GO was synthesized using a water bath method by introducing graphene; the dispersibility of ZIF-8/67 was improved, the conductivity increased, and the volume expansion phenomenon that occurs during the electrochemical deintercalation of sodium was prevented. Furthermore, vulcanization was carried out to obtain ZnS/CoS@C/rGO composite materials, which were tested for their electrochemical properties. The results showed that the ZnS/CoS@C/rGO composite was successfully synthesized, with dodecahedrons dispersed in large graphene layers. It maintained a capacity of 414.8 mAh g⁻¹ after cycling at a current density of 200 mA g⁻¹ for 70 times, exhibiting stable rate performance with a reversible capacity of 308.0 mAh g⁻¹ at a high current of 2 A g⁻¹. The excellent rate performance of the composite is attributed to its partial pseudocapacitive contribution. The calculation of the diffusion coefficient of Na⁺ indicates that the rapid sodium ion migration rate of this composite material is also one of the reasons for its excellent performance. This study highlights the broad application prospects of metal–organic framework-derived metal sulfides as anode materials for sodium-ion batteries. Full article

(This article belongs to the Special Issue Advanced Electrode Materials for Electrochemical Energy Storage and Conversion, 2nd Edition)

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11 pages, 2635 KiB

Open AccessArticle

Constructing Interconnected Microporous Structures in Carbon by Homogeneous Activation as a Sustainable Electrode Material for High-Performance Supercapacitors

by Huijie Li, Rui Ma, Feifei Chen, Danting Wang, Hongmin Zhang and Chunyang Lu

Molecules 2023, 28(19), 6851; https://doi.org/10.3390/molecules28196851 - 28 Sep 2023

Cited by 1 | Viewed by 1057

Abstract

Microporous carbon attracts attention as an electrode material for supercapacitors. However, a large number of deep and distorted mesoporous and macroporous structures are usually created by non-uniform etching, resulting in underutilized internal space. Homogeneous activation has been considered by researchers as a necessary [...] Read more.

Microporous carbon attracts attention as an electrode material for supercapacitors. However, a large number of deep and distorted mesoporous and macroporous structures are usually created by non-uniform etching, resulting in underutilized internal space. Homogeneous activation has been considered by researchers as a necessary condition for the formation of interconnected microporous structures in carbon materials. Herein, a simple strategy of hydrothermal introduction of defects followed by homogeneous activation for the preparation of microporous carbon was developed for the synthesis of electrode materials for high-performance supercapacitors. The optimized sample with defect-enriched microporous structure and large specific surface area has a specific capacity of 315 F g⁻¹ (1 A g⁻¹) in KOH solution, and the assembled symmetric supercapacitor achieves a high energy density of 7.3 Wh kg⁻¹ at a power density of 250 W kg⁻¹. This work is interesting because it not only demonstrates that rational design of electrode materials is important to boost the performance of supercapacitors, but also provides inspiration for the design of efficient supercapacitors in the future. Full article

(This article belongs to the Special Issue Advanced Electrode Materials for Electrochemical Energy Storage and Conversion, 2nd Edition)

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