Co-doped Ni3S2 hierarchical nanoarrays derived from zeolitic imidazolate frameworks as bifunctional electrocatalysts for highly enhanced overall-water-splitting activity

At present, it is critical to explore non-noble metals dual-function electrocatalyst for oxygen evolution reactions (OER) and hydrogen evolution reactions (HER) of electrolyzed water. Herein, reticular Ni(OH)2 nanosheets were synthesized on nickel foam (NF) by hydrothermal method and then ZIF-67 nanoparticles were uniformly deposited on Ni(OH)2/NF through chemical synthesis. After hydrothermal vulcanization, Co-doped Ni3S2 on NF substrate (Co–Ni3S2/NF) with trunk-branch three-dimensional composite structure was obtained, and it can act as a high-efficiency dual-function electrocatalyst to achieve full water electrolysis under 1 M KOH electrolyte. The Co–Ni3S2/NF displayed low overpotential of 240 and 120 mV (at 10 mA cm−2) for HER and OER, respectively, and had long-term electrochemical durability in alkaline conditions. The excellent catalytic activity and durability of Co–Ni3S2/NF were attributed to the lattice distortion of Ni3S2 which was caused by the Co doping derived from ZIF-67. Meanwhile, the unique trunk-branch nanoarrays resulted in Co–Ni3S2/NF with multiple exposing active sites, rapid electron transfer and the diffusion of gases/ions. Particularly, Co–Ni3S2/NF displayed a voltage of 1.69 V at 50 mA cm−2 as bifunctional electrocatalysts to the overall water electrolysis in alkaline electrolyte.