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.

Theoretical Prediction and Experimental Verification of IrOx Supported on Titanium Nitride for Acidic Oxygen Evolution Reaction

“…In addition, such a model system also allows direct verification by experimental studies, as recently demonstrated for nitride-supported Pt for the hydrogen evolution reaction. 24 Using the binding energy of *OH (* denotes adsorbed intermediates) as the OER reactivity descriptor for IrO x /TiN, the OER activity was found to be improved by increasing the Ir coverage from one to three monolayers (MLs), and the trend was confirmed by the experimentally synthesized IrO x /TiN film model catalysts.…”

Transition metal nitride catalysts for selective conversion of oxygen-containing molecules

“…35 Recent work has utilized a combination of fundamental studies of TMN thin films in ultrahigh vacuum (UHV) with electrocatalytic evaluation of the same films or thermocatalytic testing of the corresponding powder catalysts to develop correlations between the configuration and binding strength of surface intermediates and performance under realistic conditions. 36,37…”

“…It was demonstrated that by depositing 1 ML of Pt or Pd, the required overpotentials to achieve a current density of 10 mA cm −2 shifted to be similar to that of bulk Pt in acidic electrolyte. 37 TPD measurements were used to experimentally determine HBE values for Pt- and Pd-modified Mo 2 N surfaces and correlate them with HER activity. After depositing 1 ML of Pt onto Mo 2 N via physical vapor deposition, desorption temperatures of H 2 at varying heating rates were used to determine the enthalpy of atomic hydrogen adsorption or HBE.…”

“…Turaczy et al showed that for thin films in 0.1 M KOH, 1 ML Pt on Mo 2 N was able to shift the relatively high overpotential required to drive 10 mA cm −2 of current on clean Mo 2 N to that of Pt foil. 37 Other studies have used Pt NPs on Ni 3 N that outperformed the benchmark Pt/C catalyst by electrodepositing 10 nm Pt NPs onto the surface of Ni 3 N nanosheets. 122 The Pt/Ni 3 N catalyst exhibited higher HER activity than Pt/C at a current density of 50 mA cm −2 .…”