Investigating synergistic interactions of group 4, 5 and 6 metals with gold nanoparticles for the catalysis of the electrochemical hydrogen evolution reaction

Abstract

An investigation of the catalysis of the electrochemical hydrogen evolution reaction (HER, 2H⁺ + 2e⁻ → H₂) in aqueous 0.5 M H₂SO₄ electrolyte using composites consisting of gold nanoparticles (Au_NP), carbon (Black Pearl 2000) and group 4, 5, and 6 metals is presented. This study is a continuation of our earlier work (Phys. Chem. Chem. Phys., 2016, 18, 21548–21553) on molybdenum and Au_NP, which we found to interact synergistically to enhance the HER. We demonstrate here that tungsten not only also showed synergy with Au_NP, but the extent of synergy is even larger than that of the Mo–Au_NP composite. The average overpotential needed by the tungsten-based composite catalyst to drive a H₂ current density (j_H2) of 10 mA cm⁻² was 300 mV. In contrast, other metals such as Ti, Zr, V, Nb and Ta did not have any observable synergy with Au_NP. Our experimental results indicate that the absence of synergy with these non-performing composites could be related to the absorption of hydrogen into the bulk lattice of the metals to give hydrides. The strong binding of H to these metals could have also prevented their further reaction. We also propose that the aforementioned metal hydrides suppressed HER because they are ineffective for the initial proton discharge step.