Effect of surface etching on the electrocatalytic performance of Cu70(Ni,Co)30 for hydrogen evolution

A Cu-based solid solution containing nickel and cobalt with the composition Cu 70 Ni 15 Co 15 was synthesized by arc melting. Through surface preferential electrochemical etching, a porous surface layer enriched in Ni and Co was produced. The dissolution process was found to occur selectively, progressing primarily along microstructural defects - most notably grain boundaries, dislocations and stacking faults, but also to some extent through the selective dissolution of copper from the copper based solid solution Cu(15Ni,15Co). As a result of the two distinct mechanisms of surface etching, two types of pores are formed: large pores, comparable in size to the alloy crystallites, and much smaller ones (<100 nm) resulting from the extraction of copper atoms from the solid solution. The electrocatalytic properties of both the as cast and porous alloys toward the hydrogen evolution reaction (HER) were evaluated using linear sweep voltammetry and electrochemical impedance spectroscopy. The porous alloy surface exhibited significantly enhanced catalytic performance compared to pure nickel, as well as high durability during prolonged hydrogen evolution reactions.