Oxygen-evolving catalytic atoms on metal carbides.

Single-atom catalysts have shown promising performance in various catalytic reactions. Catalytic metal sites supported on oxides or carbonaceous materials are usually strongly coordinated by oxygen or heteroatoms, which naturally affects their electronic environment and consequently their catalytic activity. Here, we reveal the stabilization of single-atom catalysts on tungsten carbides without the aid of heteroatom coordination for efficient catalysis of the oxygen evolution reaction (OER). Benefiting from the unique structure of tungsten carbides, the atomic FeNi catalytic sites are weakly bonded with the surface W and C atoms. The reported catalyst shows a low overpotential of 237 mV at 10 mA cm-2, which can even be lowered to 211 mV when the FeNi content is increased, a high turnover frequency value of 4.96 s-1 (η = 300 mV) and good stability (1,000 h). Density functional theory calculations show that either metallic Fe/Ni atoms or (hydro)oxide FeNi species are responsible for the high OER activity. We suggest that the application of inexpensive and durable WCx supports opens up a promising pathway to develop further single-atom catalysts for electrochemical catalytic reactions.