Anodic Treatment of Ni-Cu Alloy in a Deep Eutectic Solvent to Improve Electrocatalytic Activity in the Hydrogen Evolution Reaction

DESs, as new-generation room temperature ILs, are very promising to perform anodic processing of different metals and alloys. We report Ni-Cu alloy (45 wt.% Ni) anodic treatment in a DES, ethaline, for the first time. It is shown that the anodic dissolution originated the formation of sparingly soluble Ni and Cu chloride salts in the near-electrode layer. Ni-Cu alloy anodic treatment in ethaline resulted in changed patterns of the metallic surface morphology. Depending on the applied electrode E, star like crystallites, with sharply pointed shapes and thorns, may appear on the anodically etched surface, and surface morphology smoothing was observed, in some cases. The Ni-Cu alloy anodic processing in ethaline, which dramatically changed its surface morphology, contributed to a considerable increase in the electrocatalytic activity towards HER in an alkaline medium. Considering favorable environmental aspects of DES use and marked improvement in electrocatalytic properties, this treatment can be further used to develop high-efficient, eco-friendly and relatively inexpensive electrocatalysts methods for water electrolysis within H 2 energy concept.