Search

In order to study the oxygen reduction activity（ORR） of Fe/Co/Ni-N doped graphenes, the influences of single metal atom and nitrogen co-doping on ORR activity of graphene were compared. The Fe/Co/Ni-N doped graphene models were established using Materials Studio, and then oxygen molecules were adsorbed respectively on the surfaces of Fe/Co/Ni-N doped graphene models. CASTEP module was used to optimize the structure of the model and simulation calculation. The adsorption energies, desorption energies and conductivities of Fe/Co/Ni-N doped graphenes were analyzed. Based on the simulation results, it is found that the ORR activity of Fe doped graphene is better than that of Co or Ni doped graphene when graphene is doped with single metal atom. As graphene is Co-doped with single metal atom and nitrogen, the ORR activity of Fe-N doped graphene is better than that of Co-N or Ni-N doped graphene, and the ORR activity of M-N4-G was better than those of M-N1-G M-N2-G and M-N3-G. [ABSTRACT FROM AUTHOR]

Beginning with the mechanism of ORR, this article integrates the preparation and application of Fe/N/C materials, analyzes the mechanism of efficient oxygen reduction electrocatalysis of Fe/N/C materials from the perspective of active sites, and elaborates on the stability issues encountered in the development of high-performance Fe/N/C materials. It further proposes suggestions and prospects for the application of Fe/N/C catalysts in fuel cells, providing references for the future development of Fe/N/C materials. [ABSTRACT FROM AUTHOR]

The development of highly efficient catalysts for oxygen reduction reaction (ORR) is the key to improve the performance of fuel cells and metal-air batteries. However, ORR is a kinetic slow reaction with high overpotential, which limits the energy conversion efficiency of fuel cells and metal- air batteries. High-entropy alloy is a new kind of alloy, which is consisted of five or more metal ele- ments with (nearly) equimolar ratios. With unique composition and structural advantages, high entro py alloy can effectively accelerate ORR kinetics and lower overpotential, showing remarkable catalytic performance toward ORR. In this paper, the structures, properties, preparation methods and applications of high entropy alloys in catalytic ORR were reviewed, and the challenges and development perspec- tives were proposed. [ABSTRACT FROM AUTHOR]

Oxygen reduction reaction is a crucial process for fuel cells. Conventional oxygen reduction catalysts are the precious metal platinum， but given the high cost of platinum， researchers want to find a low-cost alternative catalyst that is cheaper and has the equivalent catalytic activity to platinum. In previous studies， iron-nitrogen-doped graphdiyne and cobalt-nitrogen-doped graphdiyne have been studied， and they all show efficient oxygen reduction reaction activity， while nickel， with similar electronic structure with iron and cobalt， has not been studied. Therefore， in this work we design and synthesize various nickel-nitrogen-doped graphdiyne electrocatalysts using hydrogen as a substitute for graphiyne， and conduct redox electrochemical tests. The nickel-nitrogen-doped graphdiyne catalyst containing 2% nickel and melamine shows the best electrocatalytic performance for oxygen reduction. We conduct a series of physical characterizations for the catalysts： X-ray diffraction （XRD）， X-ray photoelectron spectroscopy （XPS）， transmission electron microscope （TEM）， scanning electron microscope （SEM） to further analyze their structure and morphology. It can be seen from the physical characterization and electrochemical tests that nitrogen atoms are the key to construct the catalytic active site， and nickel atoms play a vital role in improving the performance of the catalysts. With the synergistic effect of nitrogen and nickel， the nickel nitrogen-doped graphdiyne catalyst shows excellent catalytic performance， which makes it have a good application prospect. [ABSTRACT FROM AUTHOR]

Oxygen reduction reaction （ORR） is an important cathode reaction for metal-air batteries and proton exchange membrane fuel cells （PEMFCs）. It is of great significance to study non-noble metal catalysts with high activity and stability. In this paper， MIL-101（- Al-Fe） with hierarchical porous structure is innovatively used as the metal precursor template， and Fe-N-C catalysts with rich mesoporous structure are successfully prepared. Electrochemical test results show that Fe-N-C-MIL-900 shows the best ORR activity with half-wave potential of 0. 905 V in 0. 1 mol/L KOH electrolyte. The ORR electron transfer number of Fe-N-C-MIL-900 catalyst is 3. 98， and the H2O2 yield is less than 3%， demonstrating an obvious 4-electron ORR pathway. This work provides a new way to prepare hierarchically porous Fe-N-C catalysts with high ORR activity. [ABSTRACT FROM AUTHOR]

Electrochemical synthesis of hydrogen peroxide （H2O2 ）via two-electron oxygen reduction reaction （2e-ORR） is featured with cost effectiveness and environmental friendliness， and enables on-site production of H2O2 on demand. One of the key technologies is the development of safe， economical and efficient 2e-ORR catalysts. Here， the research progress in precious-metal-based catalytic materials for the synthesis of H2O2 via 2e-ORR in recent ten years is reviewed. This review starts with the fundamental mechanism of ORR， pointing out the tuning knobs of reaction pathway on precious-metal surfaces， namely，* OOH binding energy and O2 adsorption mode. The regulating methodologies of geometric structure and electronic structure of precious-metal materials are summarized and exemplified， emphasizing the importance of balanced optimization of catalytic activity and selectivity. We have also briefly introduced the lab-scale methods for performance evaluation of 2e-ORR catalysts. Finally， the challenges and prospects of H2O2 synthesis catalyzed by precious metals are discussed， especially the catalyst stability and the objective evaluation of cost. This review is expected to provide a reference for rational design of novel 2e-ORR catalysts. [ABSTRACT FROM AUTHOR]

With the increasing demand for green and efficient energy storage devices， advanced technologies for clean energy conversion have attracted close attention from researchers. Fuel cells with environmental friendliness and high energy conversion efficiency are promising alternatives to traditional energy sources. However， Pt catalysts with high commercialization degrees in the industrial catalysis field have some problems， such as high cost， poor stability and weak anti-toxicity ability， which limits the further development of fuel cells. The development of non-Pt oxygen reduction reaction （ORR） catalysts with abundant reserves， low cost and excellent performance is an effective way to improve the efficiency of fuel cells. In this paper， based on the research results at home and abroad in recent years， various types of non-Pt system ORR catalysts， including non-precious metal and non-metal catalysts， are systematically introduced. The advantages， disadvantages and modification strategies of various catalysts are summarized， and challenges and prospects for the development of ORR electrocatalysts are put forward. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) are regarded as effective precursors for the preparation of M-N-C oxygen reduction electrocatalytic materials. However, the structural collapse of MOFs during the pyrolysis limits their practical application. In this study, ZIF-67 was firstly modified by coating with the surfactant of F-127 and doping with Zn. After that, the modified Zn-ZIF-67 @ F-127 was pyrolyzed under argon atmosphere to fabricate the Co-N-C support with complete structure. By loading Pt on the surface of Co-N-C support, the Pt/Co-N-C composite catalyst for oxygen reduction reaction (ORR) was obtained. The ORR catalytic performances in the alkaline electrolyte were systematically studied. The experimental results show that the addition of F-127 can improve the morphological retention of Zn-ZIF-67@ F-127 during the pyrolysis. More importantly, the onset potential, half-wave potential, and diffusion-limited current density of Pt/Co-N-C in O2-saturated 0.1 mol·L-1 KOH are 1. 027 V, 0. 836 V, and 5. 51 mA·cm-2, respectively, which are similar to those of the commercial 20% Pt/C catalyst. The synergistic effect of Pt and Co-N-C not only exhibits a high selectivity and current density for the ORR four-electron pathway, but also shows a high stability approaching the commercial 20% Pt/C catalyst, and superior methanol resistance performance compared with the commercial 20% Pt/C in the chronoamperometry test. [ABSTRACT FROM AUTHOR]

The catalytic layers of proton exchange membrane fuel cells prepared by spraying or transfer printing methods have problems of uneven activity or easy failure of active sites. In this study, a flexible carbon nanofiber film with high conductivity was prepared by electrospinning, and then Cu with high hydrogen evolution potential was uniformly deposited on the fiber film by pulse electrodeposition to prepare Cu nanocrystal@ PtCu / carbon nanofiber film. Finally, a Cu@ PtCu / carbon nanofiber (Cu@ PtCu / CNF) catalytic film was synthesized by situ exchange reduction. The Cu@ PtCu / CNF catalytic film solves the problem of uneven activity of the catalytic layer. It can be directly used as the catalytic layer. Its morphology and structure were characterized by SEM, XRD, XPS. The electrochemical test results show that Cu@ PtCu / CNF catalytic films obtained at pH = 4 and chloroplatinic acid concentration of 0. 25 m·mL - 1 have an area specific activity of 49 m 2 ·g - 1 . After 5 000 cycles of stability testing, the electrochemically active specific surface area remains 74%, and the half-wave potential decreases by 9 mV, both better than commercial Pt / C catalysts. [ABSTRACT FROM AUTHOR]

This article introduces the basic principles and characteristics of the electro-Fenton (EF) process in detail, clarifies that cathode materials and metal catalysts are important components of the EF process, focuses on the types and modification methods of cathode materials and catalysts, and analyzes working current, electrolyte pH, air volume and other parameters on the effect of EF treatment. Finally, the application of EF process in dye wastewater treatment and possible technological breakthroughs are prospected. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide production via electrocatalytic two-electron oxygen reduction is an effective alternative to traditional centralized anthraquinone processes. However, this process depends on a catalyst with low cost, high activity and high selectivity. In recent years, SACs have been considered as potential catalysts for oxygen reduction and hydrogen peroxide production due to their nearly 100% atom utilization efficiency, tunable electronic structure, and excellent catalytic performance, but the regulation of SAC activity remains a challenge. Starting from the mechanism of the ORR, the influence of the binding strength of the active metal center and *OOH on the oxygen reduction reaction pathway is elucidated. This study systematically illustrates the effect of adjusting the structure of the SAC on the binding of the metal center to *OOH from three aspects: metal center atom, coordination atom and the surrounding environment of the active center, and reveals the activity and selectivity of H2O2 production. [ABSTRACT FROM AUTHOR]

In proton exchange membrane fuel cells, cost, performance and durability are important issues that are need to be resolved before commercialization. The main reason for fuel cell performance degradation during operation is the loss of electrochemical surface area during long-term aging or transient. These losses mainly come from the degradation of the catalyst metal and the corrosion of the carbon support. This is a continuous and irreversible process that will greatly shorten the service life of the fuel cell. In order to explore this problem, 20% (mass fraction) Pt/C catalyst is prepared based on carbon carrier etched by sulfuric acid. The morphology characterization test shows that it is uniformly dispersed and uniform in particle size, which is considered as an excellent material for long-term oxygen reduction (ORR) stability test. Next, the ORR stability test method with different cyclic voltammetry (CV) cycles is used to observe its performance degradation, and a series of physical characterizations, e. g. transmission electron microscopy (TEM), high resolution electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy (Raman), are used to further intuitively analyzed the attenuation mechanism. It is reported that the reasons for the degradation of the stability of Pt/C catalysts are mainly from the dissolution, agglomeration, oxidation and migration of Pt particles and the corrosion of carbon supports. This study elucidates the source of the impact on the stability of fuel cells during operation, and provides a reference for designing high-stability commercial ORR catalysts. [ABSTRACT FROM AUTHOR]

Zinc-air batteries (ZABs) are regarded as one of the most promising candidates for a new generation of advanced energy conversion and storage devices, while the inferior activity and stability of air cathode electrocatalysts largely hinder the widespread application of ZABs. The extensive efforts for exploring and designing high active yet stable air cathode catalysts is, therefore, indispensable for the improvement of ZABs performance. Recently, carbon-encapsulated iron-based nanoparticles have been reported to exhibit excellent oxygen catalytic performance on account of their resistance to corrosion, oxidation, and aggregation under harsh conditions, and have been widely used as cathode materials for ZABs. As a result, we systematically summarize the applications of carbon-encapsulated transition metal iron-based materials as cathode catalysts for ZABs. In this review, the basic principle of ZABs and challenges faced by air cathode catalysts are firstly expounded. Then, the research progress of the carbon-encapsulated iron-based nanoparticles electrocatalysts (such as iron-based and its alloy, carbide, oxide and phosphide, et al.) are emphatically discussed and analyzed. Finally, the future development perspectives of carbon-encapsulated iron-based electrocatalysts in the applications of ZABs are put forward. [ABSTRACT FROM AUTHOR]

With the increasing consumption of the global energy demand, the electrochemical conversion and storage of new energy sources have drawn increasing attention in scientific research. As a promising energy conversion technology, fuel cells have attracted extensive attention in academia and industry due to their high energy conversion efficiency, environmental friendliness, high power density and wide range of fuels. Especially, oxygen reduction reaction (ORR) at the cathode is considered as an important electrode reaction in fuel cells. However, several factors, including slow kinetic process, extreme dependence on noble metal platinum, and rapid degradation of catalytic performance and durability after long-term operation, have severely restricted the large-scale promotion and application of these fuel cells commercialization. Therefore, the development of low-cost, highly active and stable catalysts is of great significance to promote the commercialization. Recently, Titanium nitride (TiN), as a highly durable support, has attracted extensive attention because of its superior properties of high conductivity, high melting point, high hardness, abrasion resistance and super anti-corrosion to acid and alkaline. When the advanced TiN material with favorable morphology and porous structure, high surface area and nanostructure is used as catalyst support, the electrocatalytic performance of Pt-based catalysts will be enhanced significantly due to the improved utilization of Pt, enhanced metal-support interactions, promoted mass/charge transfer as well as corrosion resistance. Interesting, TiN has also electronic properties similar to noble metal, and exhibits superior catalytic performance and durability toward ORR, thus obtaining widely attention in non-precious metal catalysts. Based on the above analysis, this review has summarized the current preparation method and synthesis mechanism of TiN materials, and elaborated the latest research progress including TiN, transition metal-doped TiN and its carbon-based composite materials as support or catalyst toward ORR. Based on the presented progress, we finally prospect the future application of TiN materials and directions for designing and developing practical fuel cell cathode catalysts. [ABSTRACT FROM AUTHOR]

Pt and Pt-based materials are the most efficient electro catalysts for oxygen reduction reaction (ORR). Herein, Pt-Co-Ni co-doped hollow carbon sphere/tubular carbon composite catalyst (I-Co-Ni/NHCS-TUC-6()()) with Pt content of less than 4 wt% is prepared. By constructing a reasonable spatial structure of the catalyst and introducing transition metal co--doping, the Pt mass activity of I-Co-Ni/NHCS-TUC-600 for ORR is greatly improved. ORR electrochemical activity tests show that the Pt-Co-Ni/NHCS-TUC-600 reveals excellent catalytic performance comparable to commercial IC, which is specifically expressed as the ORR onset potential of ().927 V (vs RHE), half-wave potential of 0.867 V (vs RHE), limiting diffusion current density of 6.97 mA/cm2. The prepared I-Co-Ni/NHCS-TUC-600 displays broad application prospects and provides new possibilities for the research of the catalysts with low Pt loading. [ABSTRACT FROM AUTHOR]

Pt and Pt-based materials are the most efficient electro catalysts for oxygen reduction reaction (ORR). Herein, Pt-Co-Ni co-doped hollow carbon sphere/tubular carbon composite catalyst (I-Co-Ni/NHCS-TUC-6()()) with Pt content of less than 4 wt% is prepared. By constructing a reasonable spatial structure of the catalyst and introducing transition metal co--doping, the Pt mass activity of I-Co-Ni/NHCS-TUC-600 for ORR is greatly improved. ORR electrochemical activity tests show that the Pt-Co-Ni/NHCS-TUC-600 reveals excellent catalytic performance comparable to commercial IC, which is specifically expressed as the ORR onset potential of ().927 V (vs RHE), half-wave potential of 0.867 V (vs RHE), limiting diffusion current density of 6.97 mA/cm2. The prepared I-Co-Ni/NHCS-TUC-600 displays broad application prospects and provides new possibilities for the research of the catalysts with low Pt loading. [ABSTRACT FROM AUTHOR]

Ni-foam @Nitrogen doped carbon/MnO2 (Ni-foam @ NC/MnO2) integrated elec trode was synthesized by hydrothermal method and precipitation method, respectively. The phase structure and micro morphology of the composite materials were analyzed by XRD, XPS and SEM. In this work, the direct methanol fuel cell (DMFC) was assembled by Ni foam@NC/MnO2 as cathode. PtRu/C as the anode catalyst, and polymer fiber membrane as the electrolyte membrane. The integrated electrodes synthesized by the two methods showed relatively closed discharge performances at room temperature. The DMFCs could discharge stably for 18 hours at a current density of 10 mA cm -2 without significant attenuation. However, in the 60 °C tests, the maximum power density of the foamed Ni-foam@NC/MnO2 integrated electrode synthesized by hydrothermal method was 16. 67 mW cm, while the maximum power density of the electrode synthesized by precipitation method was 9. 14 mW. cm-2. This is because the decrease of oxygen concentration in hydrothermal synthesis pro moted the presence of more oxygen vacancies, and accelerated the oxygen adsorption and e lectron transfer. [ABSTRACT FROM AUTHOR]

金属-氮-碳(M-N-C)化合物作为非贵金属催化剂具有优异的氧还原(ORR)性能,在燃料电池和金属-空 气电池等电化学能源转化方面展现了广阔的应用前景。开发出能够与贵金属铂催化剂相媲美的高效且廉价的催 化剂以解决ORR缓慢动力学问题具有重要意义。选用金属有机骨架材料ZIF-67作为碳源和氮源,其中,二价 钴离子、2-甲基咪唑和高分子聚合物聚乙烯亚胺(PEI)在室温下快速原位合成催化剂,PEI不仅能避免ZIF-67的 团聚还提高了催化剂的氮含量。所制备出的纳米材料Co-N-C(ZIF-67+PEI)催化剂在碱性电解质中拥有优于商 业Pt/C的ORR性能及稳定性和抗甲醇性能。 [ABSTRACT FROM AUTHOR]

Oxygen reduction reaction exists in many kinds of energy storage devices, such as air cells and fuel cells. Commercial platinum carbon is usually used as the catalyst for oxygen reduction reaction. However, its disadvantages associated with high price and toxic limit its further development. Carbon based materials are considered to be the best substitute for platinum carbon catalyst, which has attracted the interest of many researchers. Due to the different physical and chemical properties of carbon atoms and heteroatoms, when the heteroatoms are incorporated into the carbon matrix, defects and active sites can be formed in the matrix, and then the conductivity and oxygen transport capacity can be improved, thereby improving the catalytic ability of carbon materials for oxygen reduction reaction. Therefore, this paper firstly introduces the mechanism of oxygen reduction reaction, and then introduces the preparation of various heteroatom doped carbon based oxygen reduction catalysts as well as their advantages and innovations. [ABSTRACT FROM AUTHOR]

Low-cost catalysts with high activity and acceptable stability toward oxygen reduction reaction (ORR) attract much interest and attention in recent years. Tn this work, FeN/C catalysts for ORR were synthesized via impregnation with different pyrolysis process. The effects of secondary pyrolysis in ammonia on catalysts structure and performance were investigated by various techniques, such as X-ray diffraction, N-adsorption poro-simetry, transmission electron microscope and electrochemical characterization. The catalyst underwent secondary pyn〕lysis showed obvious improved ORR activity and stability compared to the catalyst underwent one pyrolysis in argon. This was attributed to the catalyst underwent secondary pyrolysis had higher RET surface area (931.2 m'/g) and surface nitrogen content (1.67 at.%), as well as the existence of Fe.sC. [ABSTRACT FROM AUTHOR]

RuxSey/graphene catalysts are synthesized by the one-pot solvothermal method, with the RuCl3·xH2O and SeO2 as precursors and the reduced graphene oxide as carrier. The influence of ethanol and ethylene glycol on the morphology performance of the catalysts is investigated. By utilizing transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy (Raman) and rotating disk electrode (RDE) techniques, the physical property and activity for oxygen reduction reaction (ORR) of as-prepared electrocatalysts are characterized, respectively. The results suggest that RuxSey particles can be evenly dispersed on graphene layers and RuxSey/graphene catalysts prepared in ethylene glycol are well crystalized. The presence of ethylene glycol can contribute to the reduction process of graphene oxide and the increase in its specific surface area, thus leading to a relatively high catalytic activity of the catalyst upon ORR in 0.1 mol/L KOH. [ABSTRACT FROM AUTHOR]

Fuel cell is a new clean energy, but the commercial oxygen reduction reaction (ORR) catalyst is the noble metal platinum. Hence, looking for cheap, efficient ORR catalyst is the key to improve the performance of the oxygen electrode. With higher conjugated structure and better chemical stability, Metalloporphyrin complexes are excellent catalyst for ORR both in acid and alkaline solution. From Tetraphenylporphyrin cobalt (CoTPP) without any easily polymerizable functional group, the polymer thin film of pCoTPP was obtained by cyclic voltammetric electrochemical polymerization method. From the UV-vis spectra, the Soret-band and Q-bands of pCoTPP are red-shifted and their full widths at half-maximum (FWHM) are wider than CoTPP monomer. It is because pCoTPP has higher conjugated structure than CoTPP. As it turns out, the pCoTPP-modified GCE exhibits higher catalytic activity for ORR in oxygen-saturated basic solution. The role of pCoTPP has offered new research direction and field for catalyst research in ORR, and hopefully to be non -noble metal catalytic material. [ABSTRACT FROM AUTHOR]