Heterogeneous bimetallic oxysulfide nanostructure (Ni-Co) as hybrid bifunctional electrocatalyst for sustainable overall alkaline simulated seawater splitting

The design and development of high performance non-precious bifunctional electrocatalytic activity for oxygen/hydrogen evolution reaction (OER/HER) remains a significant challenge in overall seawater splitting process. Herein, we report the Co3S4/Co3O4 hybrid nanostructures catalyst with duel functions is successfully in-situ synthesized through self-templating strategy, whereas, Ninanostructure 3S2/NiO are grown on Ni foam using a facile hydrothermal reaction and post thermal annealing process. The designed self-standing Co3O4(Co3S4)/NiO(Ni3S2)/NF nanostructure (denoted as Co-Ni-S/NF) as a self-standing hybrid electrode demonstrates an excellent bifunctional electrocatalytic activity for OER and HER process in alkaline freshwater/alkaline simulated seawater as electrolyte. Taking advantage of the bimetallic synergistic effect and formation of an efficient interface layer of Ni3S2/NiO in a unique nanostructure, the resultant bifunctional electrocatalytic performance of Co-Ni-S/NF electrode for OER & HER processes are highly performed in both electrolyte conditions. Specifically, Co-Ni-S/NF hybrid electrode requires lower overpotentials of 270 mV (at 20 mV cm−2), 310 mV (at 50 mV cm−2) for OER and lower overpotentials of 239 mV (at 20 mV cm−2), 291 mV (at 50 mV cm−2) for HER in alkaline simulated seawater condition. For two-electrode based electrolyzer analyses, Co-Ni-S/NF electrode based electrolyzer demonstrates low cell voltage of 1.67 V to attain a current density of 10 mA cm−2 with stable activity of overall alkaline simulated seawater splitting process whereas hybrid electrode used as anode and cathode. Therefore, the proposed interface engineering strategy and rationally constructing electrocatalyst nanostructure via a self-templating route could be a promising opportunity to develop an active duel functional catalyst for direct seawater splitting applications. [Display omitted] •Bimetallic Co-Ni heterostructure has effectively synthesized via in situ approach.•Co-Ni oxide/sulfide offers more bifunctional activity in fresh/seawater conditions.•Oxide/sulfide heterointerface greatly exposes catalytic active sites for OER & HER.•Influential synergetic and structural effects on bifunctional activity are delved.