Molten salt strategy: A Universal Approach to Construct High-Performance Bifunctional Carbon-based Electrocatalysts for Zinc-Air Batteries

Abstract

The molten salt strategy exhibits significant advantages and potential in the construction of carbon-based electrocatalysts, including environmental protection, recyclability, promotion of graphite formation, efficient doping functionalization, and highly controllable product structures. In recent years, most explorations have focused on optimizing the oxygen reduction reaction (ORR) performance of carbon-based materials prepared by the molten salt strategy while neglecting the improvement of oxygen evolution reaction (OER) activity. As a result, such materials with a poor balance between ORR and OER cannot achieve high performance in zinc-air batteries (ZABs). In this review, we first discuss the methodology for selecting the appropriate molten salt to enhance the catalyst's ORR or OER performance. Combined with the requirements of ZABs, the standards for the electrocatalysts required for their cathodes are elaborated in detail. Additionally, the review emphasizes the latest research progress and targeted molten salt systems on versatile carbon-based electrocatalysts for the high performance of ZABs, including metal-free carbon materials, single-atom catalysts, metal clusters/carbon composite, and metal nanoparticles/carbon composite materials. For various catalysts, the mechanism by which the molten salt method enhances catalytic performance through structural modification is systematically elaborated, providing a theoretical foundation and design guidance for the selection of appropriate molten salts in different catalytic systems. Finally, we proposed some limitations and future development directions of the molten salt method and provided a feasible thought path for designing high-efficiency bifunctional catalysts.