NiSnO_xH_y/Ni₃Sn₄ Interface Built by Hydrogen Bubbles and Electropassivation for Enhanced Hydrogen Production in Alkaline Media

Heterostructure engineering has proven its efficiency in the field of water electrolysis by accelerating reaction kinetics and boosting overall activities. Here, a heterostructure interface between a metallic alloy and its corresponding oxidized species (metal oxide and oxy/hydroxide) was constructed. Ni 3 Sn 4 alloy was electrodeposited using the dynamic hydrogen bubble template (DHBT) method, followed by an electrochemical passivation process in an alkaline medium to grow a top layer of oxidized species, resulting in a heterojunction interface (NiSnO x H y /Ni 3 Sn 4 ). Electrochemical and surface analyses were employed to describe the formed interface. NiSnO x H y /Ni 3 Sn 4 electrocatalyst showed enhanced activity towards the hydrogen evolution reaction (HER) in 1 M KOH, requiring only ‒166 mV overpotential to support a current density of 10 mA cm −2 , compared to −409, −275, and −367 mV at Sn, Ni, and non-passivated Ni 3 Sn 4 films, respectively, demonstrating the prominent superior intrinsic characteristics of the developed interface. The boosted catalysis by NiSnO x H y /Ni 3 Sn 4 is presumably attributed to a promoted dissociative step of water with concurrent prevention of the poisoning of H adsorption sites by hydroxide ions generated during HER. The proposed electropassivation approach for designing heterostructure interfaces has shown effectiveness in promoting HER rate in alkaline media, besides its economic feasibility as a simple, low-cost, and binder-free method.