Morphology Controlled Synthesis of SmMn₂O₅ Nanocrystals via a Surfactant-Free Route for Zn-Air Batteries

Developing earth abundant and highly active electrocatalysts to overcome the sluggish oxygen reduction kinetics is one of the key toward the practical applications of air batteries with economic efficiency and high energy density. Herein, a shape-controlled synthesis of mullite SmMn₂O₅ is achieved through a surfactant-free one-step hydrothermal method. SmMn₂O₅ nanoparticles (SmMn₂O₅-NPs) and nanorods (SmMn₂O₅-NRs) are successfully synthesized and in half-cell tests, SmMn₂O₅-NRs perform enhanced oxygen reduction activity relative to SmMn₂O₅-NPs in terms of a more positive half-wave potential and reduced peroxide yield. Importantly, rechargeable zinc-air batteries constructed with SmMn₂O₅-NRs exhibit not only higher peak power density (217 mW cm⁻²) over commercial Pt/C catalyst (190 mW cm⁻²) but also excellent cycling stability during long-term charging-discharging test over 170 h. The facile synthesis of SmMn₂O₅-NRs together with the remarkable electrocatalytic performance endows mullite SmMn₂O₅ with great promise in replacing the precious metal as future catalysts for air batteries.