Beam intensity of N2 plasma controlled surface engineering on WO3 for enhanced hydrogen evolution and oxygen evolution

Tungsten oxide is a promising electrocatalyst for water splitting reactions, due to its flexible chemical state, strong structural malleability and good corrosion resistance. Herein, the surface engineering on WO3 was conducted by a controllable N2 plasma for enhancing the performance of water splitting reactions. Under the specific N2 plasma treatment, the surface crystalline phase and the surface morphology of the tungsten oxide can be changed, as well as the creation of oxygen vacancies. These changes lead to a greatly increased electrochemical surface area, a narrowed bandgap, and a distorted crystal lattice. For oxygen evolution reaction (OER) in 1.0 M KOH, the activity of the modified tungsten oxide electrodes presents a positive correlation with the input plasma, and an optimal overpotential of 269 mV @ 10 mA cm-2 is achieved with a Tafel slope of 122 mV dec-1. With a high N2 plasma flux, the W-N bond can be formed on the tungsten oxide surface, which contributes to the promotion of the hydrogen evolution reaction (HER) activity, and an overpotential of 93 mV @ 10 mA cm-2 in 1.0 M KOH is exhibited, and the Tafel slope largely reduced to 76 mV dec-1. Such a facile strategy provides an engineering route of preparing efficient electrodes for water splitting reactions.