Ultra-Small Abundant Metal-Based Clusters as Oxygen-Evolving Catalysts.

The oxygen evolution reaction is a crucial step in water electrolysis to develop clean and renewable energy. Although noble metal-based catalysts have demonstrated high activity for oxygen evolution reaction, their application have been limited by their high costs and low availability. Here we report the use of a molecule-to-cluster strategy to prepare ultra-small trimetallic clusters by using polyoxometalate molecule as precursors. The ultrafine (0.8 nm) transition metal clusters with controllable chemical composition are obtained. The transition metal clusters enable a high-efficient oxygen evolution through water electrolysis in alkaline media, manifested by an overpotential of 192 mV at 10 mA cm‒2, a low Tafel slope of 36 mV dec‒1 and long-term stability for 30 h electrolysis. We note however that besides the excellent performance as oxygen evolution catalyst, our molecule-to-cluster strategy provides means to achieve well-defined transition metal clusters in the sub-nanometer regime, which potentially can have impact on several other applications.