Bifunctional porous non-precious metal WO2 hexahedral networks as an electrocatalyst for full water splitting

Abstract

The demand for sustainable hydrogen production by full water splitting has sparked interest in bifunctional non-precious metal-based electrocatalysts with excellent activity and stability for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, a simple two-step procedure involving hydrothermal synthesis and subsequent annealing treatment was applied to synthesize porous WO₂ hexahedral networks supported on nickel foam (WO₂ HN/NF). The porous WO₂ HN/NF composite reached a current density of −10 mA cm⁻² at an overpotential of 48 mV for the HER and 10 mA cm⁻² at an overpotential of 300 mV for the OER in an alkaline electrolyte (1.0 M KOH). According to the density functional theory (DFT) calculations, the high catalytic performance of this materials towards the HER could be attributed to the electronic structure of WO₂ within the composite. Based on the remarkable electrochemical performance for both the HER and OER, we constructed a symmetric electrochemical water-splitting device. To afford a water-splitting current density of 10 mA cm⁻², the alkaline water electrolyzer based on WO₂ HN/NF needed a cell voltage of 1.59 V. In addition, this water electrolyzer remained stable over 48 h under continuous operation, which is as good as the performance of commercial Pt/C-based electrolyzers.