Role of Surface Oxophilicity in Copper-Catalyzed Water Dissociation

Understanding water dissociation on nonprecious metal surfaces is essential toward designing efficient catalysts for important chemical reactions such as water-splitting and carbon dioxide reduction. Hydrogen binding energy (HBE) has been proposed to be a good descriptor to predict hydrogen evolution reaction (HER) activity in alkaline electrolytes. In this work, we showed that although HBE values could predict the HER activity reasonably well, the oxophilicity of the catalyst surface also played a significant role in water dissociation. To elucidate the role of surface oxophilicity, a series of nonprecious copper-based bimetallic materials were systematically studied for HER activity in alkaline conditions. By alloying copper with small amounts of oxophilic transition metals such as Ti, Co, or Ni, a significant enhancement in HER activity was achieved in comparison to pure copper. However, if the HBE was considered as the sole descriptor, the experimentally measured HER activity trend did not match the theoretical trend as predicted by density functional theory (DFT) calculations. Further studies combining both computational efforts and experimental investigation of metal oxide/hydroxide (MO/OH) clusters deposited on Cu surfaces showed that oxygen binding energies (i.e., the oxophilicity of the dopant metal) together with HBEs should be used as descriptors to predict HER activity in alkaline conditions due to the synergistic interactions between copper and the oxophilic metal.