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 (beta), 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 beta) 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.

Automated summary

Combining noble metals with nonnoble metals is an attractive strategy to balance the activity and cost of electrocatalysts. In this study, Ir@Co3O4 as a platform electrocatalyst for the oxygen evolution reaction (OER) was thoroughly investigated. The pseudocapacitive feature of Co3O4 and the high reaction order of Ir sites synergistically contribute to the boosted OER activity of Ir@Co3O4. Additionally, the application of Ir@Co3O4 in Zn-air batteries improves the charging potential and cycle stability. This work provides clear guidance for boosting the utilization of noble metals in electrocatalysis.