Recent advances in non-precious metal-based carbon materials for enhanced oxygen reduction and evolution reactions in rechargeable zinc-air batteries

The quest for energy storage systems that are both sustainable and efficient has generated growing attention toward rechargeable zinc-air batteries (ZABs), known for their elevated theoretical specific energy, affordability, and eco-friendliness. Nevertheless, the effective application of ZABs faces challenges due to the slow kinetics associated with the oxygen reduction reaction and the oxygen evolution reaction. Traditionally, the preferred catalysts for these reactions have been platinum-group metals because of their remarkable catalytic activity and stability, but their prohibitive cost and scarcity have driven the search for cost-effective, non-precious metal (NPM)-based alternatives. NPM-based carbon materials, including metal-organic framework derivatives, metal-doped carbons, carbon nitrides, and heteroatom-doped carbons, have emerged as promising candidates for replacing platinum-group metals in ZABs. These materials offer high specific surface areas, tunable morphologies, and the ability to incorporate multiple active sites through doping with elements such as nitrogen (N), sulfur (S), phosphorus (P), and boron. The enhanced transfer of electrons and mass transport is facilitated by these attributes, resulting in better catalytic performance for both the oxygen reduction reaction and oxygen evolution reaction. This review highlights recent advancements in the design and synthesis of NPM-based carbon catalysts, detailing strategies to enhance their performance and providing examples of high-performance catalysts. These catalysts, especially when applied in solid-state ZABs, offer significant improvements in terms of efficiency and stability, making them promising candidates for next-generation energy storage systems. The future outlook includes the optimization of synthesis parameters and exploration of wider applications for these advanced electrocatalysts.