Rational manipulation of 3D hierarchical oxygenated nickel tungsten selenide nanosheet as the efficient bifunctional electrocatalyst for overall water splitting

The development of a bifunctional hierarchical nanostructure catalyst with high activity, low cost, excellent reversibility, and binder-free is an emerging key demand in industrial application for overall water splitting. In this work, a new strategy was employed for the rational design of 3D hierarchical oxygenated nickel tungsten selenide on conductive nickel foam substrate (O–Ni_1−xW_xSe₂/NF) by a low-cost hydrothermal process, followed by a partial controlled-selenization process. Owing to the enriched oxygenated intermediates and abundant active sites with nanoporous networks, the optimal O–Ni_0.5W_0.5Se₂ hierarchical nanostructure shows excellent catalytic activities for hydrogen evolution and oxygen evolution reactions, which exhibit a low overpotential of ∼ 109 and 238 mV at 20 mA cm⁻², with remarkable durability. Most significantly, the O-Ni_0.5W_0.5Se₂||O-Ni_0.5W_0.5Se₂ electrolyzer required a small cell voltage of ∼ 1.56 V at 10 mA cm⁻². The present study suggests a new strategy for designing highly active hierarchical 3D oxygenated enriched metal selenide as a durable bifunctional electrocatalyst.