Electrodeposition and characterization of Ni-MoO2 composite coatings as cathodes for the hydrogen evolution reaction in alkaline solution

Abstract

Composite Ni-MoO2 coatings were prepared and characterized with respect to their possible application as electrocatalysts for the hydrogen evolution reaction (HER) in alkaline solution. The composites were electrodeposited onto Ni meshes from an ammonium chloride Ni solution with suspended MoO2 particles in simulated industrial conditions for production of commercial cathodes. The influence of the concentration of MoO2 particles in the solution and deposition current density on the morphology, chemical and phase composition of obtained coatings was investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). Catalytic activity for the HER of the coatings was examined by polarization measurements in a 32 wt. % NaOH solution at 90?C and compared to the activity of the commercial De Nora?s cathode (DN). It was shown that the most active Ni-MoO2 coating exhibits better polarization characteristics for the HER than the DN cathode. The mechanism of the HER on the specified Ni-MoO2 coating was investigated in 8 mol dm-3 NaOH at 30?C by means of steady-state polarization measurements and an electrochemical impedance spectroscopy (EIS) method. Based on the theoretical interpretation of the experimental data, rate constants of the three individual steps of the HER were determined and the source of catalytic activity of the coating was elucidated.