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

An investigation of the catalysis of the electrochemical hydrogen evolution reaction (HER, 2H+ + 2e- → H2 ) in aqueous 0.5 M H2 SO4 electrolyte using composites consisting of gold nanoparticles (AuNP ), 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 AuNP , which we found to interact synergistically to enhance the HER. We demonstrate here that tungsten not only also showed synergy with AuNP , but the extent of synergy is even larger than that of the Mo-AuNP composite. The average overpotential needed by the tungsten-based composite catalyst to drive a H2 current density (jH2 ) 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 AuNP . 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.