Abstract
Rechargeable Zn-air batteries (ZABs) are promising energy-storage systems owing to their high theoretical energy density, low cost, and intrinsic safety. However, their practical application remains limited by the sluggish oxygen evolution reaction (OER) during charging, resulting in large overpotentials and poor energy efficiency. Recently, replacing OER with small-molecule oxidation reactions (SMORs) has emerged as an effective strategy to reduce charging voltage and improve round-trip efficiency. Compared with OER, the electrooxidation of small molecules such as methanol, ethanol, urea, and glycerol occurs at lower potentials and generally exhibits faster reaction kinetics under alkaline conditions. In addition to energy-efficient charging, SMOR-assisted ZABs also provide opportunities for wastewater treatment and biomass valorization. This review critically examines the fundamental principles, recent advances, and key challenges of SMOR-assisted ZABs, providing perspectives for their practical implementation.