Thin Nickel Layer with Embedded WC Nanoparticles for Efficient Oxygen Evolution

Developing active and stable electrocatalysts for the oxygen evolution reaction (OER) is essential to enhance the efficiency of water splitting. Herein, we report a nickel/tungsten carbide (Ni/WC) composite catalyst in which WC nanoparticles are embedded underneath thin Ni layers as a highly active OER catalyst in an alkaline electrolyte. The thin Ni layer has a modulated electronic structure stemming from the interaction with the WC. The Ni/WC composite exhibits excellent OER activity and durability in a 1 M KOH solution. The turnover frequency of the Ni/WC composite (0.58 s(-1)) is increased by approximately 5.8 times relative to that of the Ni nanoparticles (0.10 s(-1)). The significant increase in catalytic activity of the Ni/WC composite can be attributed to the adsorption property change originating from the interaction between the Ni layers and the WC nanoparticles. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculation results show that the electronic structure of the Ni layers can change due to electron transfers from the WC nanoparticles to the Ni layer across their interfaces. This electronic structure change reduces the kinetic barrier of the rate-determining step of the OER pathway by lowering the O* binding energy that impedes the OER kinetics. As a result, the overall OER on the Ni/WC surface is accelerated. These findings suggest a unique strategy by which to enhance the catalytic activity of the OER in an alkaline electrolyte.