A review of advancements in theoretical simulation of oxygen reduction reaction and oxygen evolution reaction single-atom catalysts

Aqueous electrolytes metal-air batteries have garnered widespread attention owing to their safety, low cost, and non-toxic properties. Yet, their development is hindered by slow reaction efficiency. To address this issue, extensive exploratory work has been conducted by researchers. Among them, single-atom catalysts (SACs) represent a significant research direction and a hot topic for the metal-air battery catalysts. Theoretical calculations have been instrumental in predicting and screening high-activity SACs. Besides, the efforts have been made to investigate the performance of SACs for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, we specifically analyze the development and prospects of SACs for ORR/OER. The theoretical research on SACs can be divided into two stages. The first stage involves exploring the mechanism of ORR/OER reactions, also known as ideal condition theoretical simulations. The exploration scope can be categorized into four types: 1) transition metals loaded on different substrates; 2) different transition metals loaded on the same substrate; 3) the impact of the coordination environment on the catalytic efficacy of SACs; and 4) the application of machine learning in the field of catalysts. The second stage involves simulating experimental environments, where researchers begin to consider the effects of voltage, solvation, pH, surface states, and microscopic molecular dynamics on catalysts. This work comprehensively reviews the current status of SACs for ORR/OER and provides suggestions for the development of SACs in the next stage.