Ni-Mo alloy nanostructures as cathodic materials for hydrogen evolution reaction during seawater electrolysis

摘要

In the case of hydrogen production involving seawater electrolysis, one of the main targets is to develop more active cathodic materials, to optimize the efficiency of hydrogen evolution reaction (HER) and, by doing so, enhance the overall energy efficiency of electrolysis. Thus, to develop suitable HER electrocatalysts either an increase of the electrode active surface area or a design of a material having high intrinsic catalytic activity should be taken into consideration, both of them decreasing the HER overpotential. In the present work, various Ni-Mo alloy nanostructures (10-40 wt% Mo) have been prepared involving electrochemical deposition from aqueous and deep eutectic solvent (DES)-based electrolytes as potential cathodic materials suitable for hydrogen evolution reaction during water electrolysis. The electrocatalytic activity of the obtained layers has been investigated using real seawater electrolyte. The determined Tafel slopes suggested that the electrodeposited Ni-Mo alloy coatings follow an HER mechanism controlled by the Volmer reaction step. The EIS results indicated that the use of choline chloride-based ionic liquids as electrolytes facilitated Ni-Mo alloy coatings showing a significant increase in surface roughness. Studies of the intrinsic activity showed that the main contribution towards the apparent activity comes from the increase of the real surface area, although a slight increase of the intrinsic electrocatalytic activity in the case of Ni-Mo alloy coatings electrodeposited on Ni foam was also noticed. These results showed that Ni-Mo alloy coatings electrodeposited from the novel electrolytes based on choline chloride-urea-citric acid ternary mixtures associated with a porous substrate may represent a promising technological approach to build cathodic materials suitable for seawater electrolysis.