Electronic engineering to enhance bifunctional activity of carbon-based single-atom catalysts in rechargeable zinc-air batteries

As one of the most promising candidates for green energy storage and conversion, rechargeable zinc-air batteries (ZABs) are usually subject to sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at air have been attracting wide attention for electrocatalytic ORR/ OER processes. Despite the tremendous efforts on studying C-SACs, their bifunctional catalytic activity still has room for further improvement. Electronic engineering is an effective method to optimize the adsorption/desorption behaviors of the reaction intermediates on the active sites for further boosting the ORR/OER catalytic kinetics. In this review, we systematically summarize recent progresses of electronic engineering for enhancing the bifunctional catalytic activity of C-SACs within the context of the restructuring coordination environment, the carbon substrate effect, and the second metal species synergism, as well as profoundly discuss the relationship between the optimized structure of active site and enhanced electrocatalytic performance. Finally, the challenges and perspectives of C-SACs toward commercial ZABs are proposed.