Oppositely directed epitaxial growth of nickel (oxy)hydroxide amorphous oxygen-deficient skin for effective oxygen...

The amorphous nickel (oxy)hydroxides (NiO_x(OH)_y) with enriched oxygen vacancies (O_v) grown on the surface of Ni₃S₂ substrate were designed to boost oxygen evolution reaction (OER) activity. The achieved electrocatalysts showed excellent OER performance with η_j10 of 130 mV, η_j100 of 256 mV, and stability for at least 375 h, outperforming the commercial RuO₂ catalysts and most of the state-of-the-art OER catalysts. A new universal stoichiometric mismatch method was developed to synthesize this special structure-by etching low-sulfur-content sulfides in an alkaline aqueous environment to guide the formation of oxygen-deficient amorphous metal oxides. Further, to obtain well-direction low-sulfur nickel sulfide, a novel reverse epitaxial growth method was developed. In this method, in-situ prepared [001]- direction nano Bi₂S₃ needles were deposited on nickel foam, guiding the substrate to transform into [001]-direction Ni₃S₂ while causing Bi to detach from the surface. Here, the as-obtained amorphous oxygen-deficient material effectively activates lattice oxygen, and the oxygen vacancies along with the amorphous character at the Ni₃S₂-NiO_x(OH)_y interface trigger a unique charge transfer effect, fully activating the surface to promote OER.