Electrodeposition of mesoporous Ni-Mo-O composite films for hydrogen evolution reaction

We have prepared mesoporous composite Ni-Mo-O films (Ni-Mo-O MCFs) on conductive Au substrates via electrodeposition with the help of a soft template, and determined the optimal electrodeposition conditions of the films such as ethanol concentration, rotate speed, and current density. The composition of the films can be adjusted with the deposition current density and ethanol content to a Ni content within 50-75 wt.%. Mesoporosity is constantly present and homogeneously distributed on the films with a pore diameter about 5 nm-10 nm, and the film thickness is uniform at 200 nm. We propose a mechanism for the Ni-Mo-O MCFs formation, and evaluate the electrocatalytic activity for hydrogen evolution reaction (HER). Results show that the Ni-Mo-O MCFs display an improved active surface area and higher catalytic activity for HER, and excellent stability for over 70 h in 1 M KOH solution. The overpotential can reach a value of 222.8 mV at 10 mA cm-2 current density, with a Tafel slope of 141.66 mV dec-1, compared to bare substrate (558.57 mV at 10 mA cm-2). The improved electrocatalytic performance of Ni-Mo-O MCFs is attributed to the synergetic effect of the larger actual surface and the enhanced electrochemical activity of the films.