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High Electrocatalytic Response of Ultra-refractory Ternary Alloys of Ta-Hf-C Carbide toward Hydrogen Evolution Reaction in Acidic Media

Abstract:

Transition metal carbide alloys are promising materials to replace platinum as electrodes in electrocatalysts toward the hydrogen evolution reaction (HER). Although tantalum hafnium carbides (Ta-Hf-C) have shown outstanding refractory and structural properties, there is no clear role of their electrochemical efficiency. Here we report on the electrochemical activity of such thin films, (Ta2C)(100-x)%·(Hf2C)(x)%, x = 100, 70, 30, and 0, deposited by magnetron sputtering. Grazing incidence X-ray diffraction showed no evidence of phase segregation, and XPS confirms the well-controlled stoichiometry of the electrodes. The HER kinetics was studied in strong acidic conditions, and it was found that the (Ta2C)70%·(Hf2C)30% was the most active material toward HER in this acid media and displayed an onset overpotential of -198 mV vs NHE and a Tafel slope of 129 mV·dec-1. Our results suggest that the strong affinity of Hf-C toward oxygen reduction reaction could be responsible for the high catalytic response and strong oxidation resistance of the ternary carbide alloys. Finally, we show that, in fact, the Ta-Hf-C alloys can be competitive materials toward HER.