Codeposition of Nanocrystalline Co-Mo Catalysts with a New Fluffy Microstructure for Hydrogen Evolution Reaction Based on N,N-Dimethylformamide and Ethylene Glycol System

Abstract

The codeposition behavior of Co(II) and Mo(VI) in N,N-dimethylformamide(DMF) and ethylene glycol(EG) system is observed using cyclic voltammetry (CV). The result implies that the mechanism of Co-Mo codeposition is typical induced deposition, while containing ordinary deposition process. Mo(VI) species in the system can suppress the reduction of Co(II) and its effect can be improved as the increase of Mo(VI) concentration, however, Co(II) species can promote the reduction of Mo(VI) and the effect can also be improved as the increase of Co(II) concentration. These Co-Mo films are characterized using EDS, XRD and SEM. SEM micrographs indicate that all these films exhibit a fibrous surface morphology with a new fluffy microstructure without any nodules or spherical structure. XRD pattern reveals that the Co-Mo film is a Mo solid solution in Co, or the Mo presents as agglomerates in the lattice of Co. Moreover, the feature peak of the film with a preferred orientation direction and the average size of crystalline grain is calculated to be about 9.5 nm. In addition, the electrocatalytic activity for hydrogen evolution reaction (HER) on the prepared Co-Mo films surface is investigated using linear sweep voltammetry (LSV)，electrochemical impedance spectra (EIS) and chronopotentiometry techniques. These results indicate that its electrocatalytic activity can be improved as the increase of Mo content from 1.02 to 2.84 wt% in these films and the prepared Co-Mo film with 2.84 wt% Mo presents a high electrocatalytic activity and stability for HER with an overpotential of 81 mV at 10 mA cm -2 in 1 M KOH solution.

Keywords: Thin films, Metals and alloys, Crystal growth, Catalysis, Electrochemical reactions.