Alloying Tungsten Carbide Nanoparticles with Tantalum: Impact on Electrochemical Oxidation Resistance and Hydrogen Evolution Activity

Metal-terminated bimetallic carbide nanoparticles (NPs) of tungsten and tantalum are synthesized in a monodisperse particle size distribution of 2-3 nm. The bimetallic particles feature enhanced electrocatalytic behavior with respect to the monometallic composition. X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements indicate that the Ta0.3W0.7C NPs consist of a well-mixed random alloy featuring a compressed lattice that favorably impacts stability and catalytic activity. Electrochemical testing shows that the incorporation of 30% tantalum into the tungsten carbide lattice increases the electrochemical oxidation resistance of the NPs. The onset of surface passivation in 0.5 M H2SO4 shifted from +0.2 V vs RHE to +0.45 V vs RHE, and the maximum surface oxidation current shifted from +0.4 to +0.75 V vs RHE. The activity toward hydrogen evolution (HER) of the carbon-supported Ta0.3W0.7C NPs is preserved relative to the activity of unmodified carbon-supported WC NPs. The increase in electrochemical oxidation resistance is attributed to the presence of surface Ta moieties as determined by X-ray photoelectron spectroscopy (XPS) while the preservation of the HER activity is attributed to the observed lattice compression.