Correlating Experimentally Determined Hydrogen Binding Energy with Hydrogen Evolution Activity over Metal Monolayers on Molybdenum Nitride

Abstract: It is well established that the hydrogen binding energy (HBE) is a key descriptor for hydrogen evolution reaction (HER) activity, and such a relationship is a useful tool for searching efficient and cost-effective HER catalysts. However, in almost all cases, the HBE values are obtained from density functional theory (DFT) calculations. In this study, temperature-programmed desorption (TPD) was used to experimentally determine the HBE values of metal monolayers supported on molybdenum nitride (Mo₂N), and electrochemical measurements were performed on the same surfaces. Combined DFT and kinetic Monte Carlo (kMC) simulations were used to validate the trend observed with TPD and the electrochemical HER activity. Depositing one monolayer of Pt on Mo₂N led to similar HBE values seen for bulk Pt, and electrochemical measurements showed that monolayer Pt on Mo₂N had HER activity similar to that of bulk Pt. Similar studies were also performed for monolayer Pd on Mo₂N to confirm the correlation. This work also demonstrates that Mo₂N is a promising support to reduce the precious metal loading in HER catalysts.