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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]

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]

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]

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]

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]