Non-noble metal composite cathodes for hydrogen evolution. Part I: The Ni–MoOx coatings electrodeposited from Watt’s type bath containing MoO3 powder particles

In this work the Ni–MoOx coatings have been prepared and characterized in view of their possible application as electrocatalysts for hydrogen evolution reaction (HER) in alkaline solution. The procedure of deposition of Ni–MoOx coatings from the Watt’s type bath containing MoO3 powder particles onto Ni mesh, under the conditions of simulated industrial deposition conditions for commercial cathodes, has been presented. The morphology of the obtained coatings was investigated by SEM, the composition by EDS and the phase composition by XRD techniques. The polarization characteristics for hydrogen evolution on the obtained Ni–MoOx coatings were investigated in the 32 wt.% NaOH at 90 °C and compared with the one recorded for the commercial De Nora’s coating (DN). It was shown that the best Ni–MoOx coating exhibits almost identical polarization characteristics as the commercial one. By the cross section and XRD analysis of deposited samples it was confirmed that MoO3 powder particles were not occluded by the Ni deposit and that molybdenum species were deposited from the molybdate ions formed by dissolution of MoO3, following the mechanism of induced co-deposition. The reaction mechanism for MoO3 phase deposition has also been proposed.