Recent advances in bifunctional carbon-based single-atom electrocatalysts for rechargeable zinc–air batteries

Abstract

Rechargeable zinc–air batteries (R-ZABs) have substantial potential for future large-scale applications owing to their sustainability, intrinsic safety, and high energy density. However, R-ZABs still lag behind the remarkable success of lithium-ion batteries (LIBs) to date. A crucial factor in advancing sustainable R-ZABs is the development of efficient bifunctional oxygen electrocatalysts, since they are currently constrained by the slow kinetics of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) at the air electrodes. Recently, carbon-based single-atom catalysts (C-SACs) have emerged as leading candidates among available oxygen electrocatalysts due to their high atom efficiency, adaptable structures, and outstanding catalytic activity. The growing interest in bifunctional C-SACs necessitates a thorough exploration of their reaction mechanisms and strategies for design and modification toward effective enhancement of ORR and OER performance. In this review, we begin by outlining the fundamental composition and reaction mechanisms of R-ZABs. We then delve into six atomic-scale modulation strategies of C-SACs in detail, emphasizing the relationship between structure and performance to aid in the development of highly efficient bifunctional electrocatalysts. The fundamental insights into the dynamic structural changes and the mechanisms of ORR/OER for C-SACs are presented by integrating in situ and/or operando characterizations with theoretical calculations. We also provide an overview of the latest advancements in C-SACs for sustainable R-ZABs, focusing on different types of carbon precursor and the impact of carbon nanostructures on electrocatalytic performance. Finally, we discuss future perspectives and challenges associated with C-SACs in R-ZABs. This review aims to offer practical and inspiring guidance for the exploration of optimal C-SACs and further enhancement of sustainable R-ZAB performance.