Trends in Hydrogen Evolution Activity of Metal‐Modified Molybdenum Carbides in Alkaline and Acid Electrolytes

Abstract Relatively high surface area nanocrystalline molybdenum carbide (Mo 2 C) was modified with 5 wt % silver, copper, nickel, platinum, and palladium nanoparticles and subsequently assessed for its hydrogen evolution reaction (HER) activity in alkaline and acid electrolytes. Density functional theory (DFT)‐calculated hydrogen binding energies predicted that Pt–Mo 2 C and Pd–Mo 2 C should be most active, which was confirmed with experimental results. Similar activity trends were observed at both high and low pH values, with Cu–Mo 2 C being the least active. X‐ray photoelectron spectroscopy (XPS) confirmed that metal particles remained on the sample before and after HER testing. Pt‐modified nanocrystalline Mo 2 C showed superior HER activity compared with Pt‐modified commercial Mo 2 C, making it a potential replacement for bulk Pt in alkaline membrane electrolyzers. The positive effect on the HER activity of the metal contact with non‐passivated Mo 2 C surfaces was also demonstrated.