Modulated Electronic Structure of Co₃O₄ by Single Atoms for Efficient Anodic Oxygen Evolution in Acid

The challenge of the practical application of a water electrolyzer system lies in the development of low-manufacturing cost, highly active, and stable electrocatalysts to replace the noble metal ones, in order to enable environmentally friendly hydrogen production on a large scale. Herein, a facile method is proposed for boosting the performance of Co₃O₄ through the incorporation of large-sized single atoms. Due to the larger ionic radius of rare earth metals than that of Co, the incorporation elongates the bond length of Co─O, resulting in the narrowed d-p band centers and the high spin configuration, which is favorable for the interaction and charge transfer with absorbent (*OH). As a result, the Ce-incorporated Co₃O₄ with the longest Co─O bond length exhibits the best oxygen evolution reaction (OER) performance, specifically, the turnover frequency is over 17 times higher than that of pristine Co₃O₄ nanosheet under an overpotential of 400 mV. Powered by a commercial Si solar cell, a two-electrode solar water-splitting device combining Ce-incorporated Co₃O₄ and Pt delivers a solar-to-hydrogen conversion efficiency of 13.53%. The strategy could provide a new insight for improving the performance of OER electrocatalysts in acid toward practical applications.