Understanding and tuning the hydrogen evolution reaction on Pt-covered tungsten carbide cathodes

Understanding and tailoring the interactions between hydrogen (H) atoms and catalytic surfaces is critical to developing electro-catalysts with less platinum (Pt). Tungsten carbide (WC) is a possible valence isoelectronic substitute for Pt. Using first-principles quantum mechanics calculations, we systematically investigate H binding to WC(0001) and Pt(111) surfaces. Moreover, inspired by recent experiments on hybrid monolayer-Pt/WC catalysts, we study H adsorption on these hybrid surfaces. We consider both W and C terminations and vary the number of Pt layers. We predict that the H binding energy (HBE) plateaus rapidly with the number of Pt layers and that a monolayer of Pt on a WC substrate has a similar HBE to that of pure Pt. This corroborates the experimental observation that the two systems exhibit similar electrochemical activities. Increasing the number of Pt layers leads to a slight increase in the HBE and a projected decrease in catalytic activity. Through various electronic structure analyses, we show that the similarity in activities is due to an intrinsic alteration of the character of the Pt/WC surface rather than a similarity to the pure Pt surface. Our findings provide guidance for tuning parameters that affect catalytic activity by controlling WC surface termination and Pt overlayer thickness.