Carbon-based electrocatalysts for rechargeable Zn-air batteries: design concepts, recent progress and future perspectives

With increasing interest in energy storage solutions, rapid progress has been made by researchers in the area of rechargeable Zn-air batteries (R-ZABs), which offer multiple advantages including high energy density, favorable flexibility, safety, and portability. Within R-ZABs, the air cathode integrated with bifunctional electrochemical catalysts plays a critical role in achieving a long lifespan and high energy efficiency. Recently, numerous studies confirmed that carbon-based catalysts are viable candidates for bifunctional electrochemical catalysts due to their low cost, high conductivity, high specific surface area, adjustable electronic structure, and rich morphological features. It is useful to understand the structural design strategy of bifunctional carbon-based electrocatalysts to promote the performance of R-ZABs. In this review, we first illustrate the basic configuration and reaction mechanisms of R-ZABs and the current challenges of bifunctional electrocatalysts. Furthermore, the design concept of carbon materials, including supporting engineering, doping engineering, defect engineering, and interface engineering, is discussed in detail. Based on the concept, different types of carbon materials are introduced in terms of atomic adjustment, structural design, synergistic effect, and application in R-ZABs, providing fascinating insights into the design and selection of bifunctional carbon-based electrochemical catalysts. Finally, perspectives and challenges of carbon-based R-ZABs are thoroughly discussed to provide feasible and inspiring research opinions for further improving battery performance.