Recent progress, developing strategies, theoretical insights, and perspectives towards high-performance copper single atom electrocatalysts

One of the urgent and challenging topics in diversified sustainable energy conversion and storage devices is the development of high-performance, low-cost, and high-durability electrocatalysts. M-N-C (M 1/4 transition metals) catalysts become one of the most promising electrocatalysts due to its ability to maximize the utilization of active atoms and combine the merit of homogeneous and heterogeneous catalysis. Cu-N-C catalysts have been triggered recently because of not only their robust catalytic ac-tivity and efficiency in various electrochemical reactions (e.g. oxygen reduction/evolution, CO2 reduction, and nitrogen reduction) but also the avoidance of Fenton reaction and improved durability in acid environment. In this review, first an effort is made to summarize the development of Cu-N-C catalysts including preparation, characterization, performance, application, and theoretical exploration. Then, the performance-improving strategies are discussed in terms of the coordination environments of the re-action center and various CuNx fragments, as well as the reaction mechanism and selectivity, based on free energy diagram and electron structure analysis. Finally, the problems, challenges, and opportunities of Cu-N-C catalysts are discussed, providing a perspective for future studies. This review not only gives insights into understanding of the electrochemistry mechanism of Cu-N-C catalysts but also encourages more efforts in the practical application promptly. (C) 2021 Elsevier Ltd. All rights reserved.