Facile synthesis of Cu_xS coated electrodes for the efficient hydrogen evolution reaction

A facile transformation of copper substrates into Cu_xS coated electrodes for the improved electrochemical production of hydrogen was reported. The utilization of sulfide-mediated underpotential oxidations of copper led to the simultaneous formation of Cu_xO nanoparticles at the deployed copper counter electrode, doubling the efficiency of this modification method. Equally significant, our experiments show that sizes of the thus-synthesized nanoparticles could be conveniently controlled by adjusting the relative surface area of the working and counter electrodes. Characterizations with scanning electron microscopy show that the Cu_xS deposits have a distinct pine leaf shape or a spherical morphology, depending on the electrochemical parameters used in the synthesis. The as-prepared electrodes exhibit promising catalytic performance in the electrochemical production of hydrogen, where the onset potential of Cu_xS coated electrode was found to be around – 90 mV (vs RHE) and the slope of Tafel plot was about 100 mV/Dec. The improved performance is attributed to the in-situ modification that ensured better and more intimate interconnection between the Cu_xS/Cu_xO coating and copper substrate, facilitating charge transfer.