Development of Nanostructured NiMo Oxides for Oxygen Evolution Reaction.

Water electrolysis is a method of splitting water molecules into their O₂ and H₂ components and is an imperative part of green hydrogen production. The sluggish oxygen evolution reaction (OER) is a half reaction that requires an electrocatalyst to improve the overall process. Green hydrogen has many applications including hydrogen fuel-cells, hydrogen feedstocks, and alternative fuels. Recurring electrocatalyst metals used for this half reaction include Ni, Fe, Co, and Mn. These metals have been combined with numerous other transition metals for overall improvement of the reaction. We aim to expand the collection of knowledge on promoters possible for the NiO electrocatalyst for increased stability, selectivity, and activity. In this study, the synthesis of a Ni-Mo metal oxide electrocatalysts with varying molar ratios and synthesis methods was studied to observe the differences in OER activities. All catalysts were synthesized through hard templating methods, using SBA-15 as a support. The electrocatalysts synthesized included a Ni₄MoO₄, Ni₈MoO₄, and Mo-doped NiO catalyst. Reflection X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis, Fourier-Transform Raman Spectroscopy, and energy-dispersive X-ray analysis (EDX) are used to characterize the prepared materials. Tafel slope, Nyquist plots, and cyclic voltammetry measurements are considered for the OER evaluation. The experimental results show the modifications necessary to utilize hard templating methods with Mo, as well as the resulting material if these modifications are neglected. This is especially highlighted through the XRD and EDX data. The OER screening showed that the Ni₈MoO₄ electrocatalyst was overall the most efficient based on an evaluation of the overpotential, the current density, the resistance, and the Tafel slope. Our approach to synthesize Ni-Mo-O electrocatalysts will provide an evaluation of the addition of molybdenum to the NiO electrocatalyst for the progression of efficient OER reactions.