Bridging the Charge Accumulation and High Reaction Order for High-Rate Oxygen Evolution and Long Stable Zn-Air Batteries

Combining noble metals with nonnoble metals is an attractive strategy to balance the activity and cost of electrocatalysts. However, a guiding principle for selecting suitable nonnoble metals is still lacking. Herein, a thorough mechanistic study on the platform oxygen evolution reaction (OER) electrocatalyst of Ir@Co₃O₄ to deeply understand the synergy between Ir and Co₃O₄ for the boosted OER has been carried out. It is demonstrated that the pseudocapacitive feature of Co₃O₄ plays a key role in accumulating sufficient positive charge [Q], while the Ir sites are responsible for achieving a high reaction order (β), synergistically contributing to the high OER activity of Ir@Co₃O₄ through the rate law equation. Specifically, Ir@Co₃O₄ displays a low overpotential of 280 mV at 10 mA cm⁻² with a small Ir loading of 1.4 wt%. Ir@Co₃O₄ is further applied to Zn-air batteries, which enables a low charging potential and thus alleviates the oxidative corrosion of the air electrode, leading to improved cycle stability of 210 h at 20 mA cm⁻²_. This work demonstrates that anchoring active noble metal sites (for high β) on pseudocapacitive supports (for high [Q]) is highly favorable to the OER process, providing a clear guidance for boosting the utilization of noble metals in electrocatalysis.