Functional Oxides Research Letter Elucidating the synergistic mechanism of nickel–molybdenum electrocatalysts for the hydrogen evolution reaction

Nickel–molybdenum (Ni–Mo) materials are widely used functional oxide catalysts for the hydrogen evolution reaction. In this work, we investigate the high activity of Ni–Mo by depositing size-controlled Ni nanocrystals (NCs) onto Mo substrates. We observe a synergistic increase in catalytic activity that does not scale with the Ni–Mo interface length. This evidence points to a bulk electronic interaction of the two metals that is separate from the mechanism of enhancement seen in conventionally co-deposited Ni–Mo electrocatalysts. In addition to elucidating the catalytic behavior of the Ni–Mo system, this work offers a general NC-based paradigm for investigating fundamental interactions and synergistic effects in electrocatalytic materials.