A new catalyst, prepared by a simple physical mixing of ruthenium (Ru) and tungsten (W) powders, has been discovered to interact synergistically to enhance the electrochemical hydrogen evolution reaction (HER). In an aqueous 0.5 M HSO electrolyte, this catalyst, which contained a miniscule loading of 2-5 nm sized Ru nanoparticles (5.6 μg Ru per cm of geometric surface area of the working electrode), required an overpotential of only 85 mV to drive 10 mA/cm of H evolution. Interestingly, our catalyst also exhibited good immunity against deactivation during HER from ionic contaminants, such as Cu (over 24 h). We unravel the mechanism of synergy between W and Ru for catalyzing H evolution using Cu underpotential deposition, photoelectron spectroscopy, and density functional theory (DFT) calculations. We found a decrease in the d-band and an increase in the electron work function of Ru in the mixed composite, which made it bind to H more weakly (more Pt-like). The H-adsorption energy on Ru deposited on W was found, by DFT, to be very close to that of Pt(111), explaining the improved HER activity.

acMolybdenum nitride has been recently reported to interact synergistically with gold to show an enhanced activity for the electrochemical hydrogen evolution reaction (2H + + 2e À -H 2 , HER). In this work, we elucidated the roles of nitrogen, carbon, molybdenum and gold on this observed phenomenon.Composites of Mo-based compounds, carbon black (black pearl 2000) and/or Au nanoparticles (Au NP ) were prepared, and their activities for the HER in a 0.5 M H 2 SO 4 electrolyte were measured using linear sweep voltammetry. We show and discuss here for the first time that, while the presence of carbon is necessary for the synergy phenomenon, the nitrogen atoms present in the compounds play no apparent by the mixed metal composites is proposed and discussed.

An investigation of the catalysis of the electrochemical hydrogen evolution reaction (HER, 2H + 2e → H) in aqueous 0.5 M HSO electrolyte using composites consisting of gold nanoparticles (Au), 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, which we found to interact synergistically to enhance the HER. We demonstrate here that tungsten not only also showed synergy with Au, but the extent of synergy is even larger than that of the Mo-Au composite. The average overpotential needed by the tungsten-based composite catalyst to drive a H current density (j) of 10 mA cm was 300 mV. In contrast, other metals such as Ti, Zr, V, Nb and Ta did not have any observable synergy with Au. 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.