In-situ etching synthesis of 3D self-supported serrated Ni-WO3 for oxygen evolution reaction

The slow kinetics of oxygen evolution reaction (OER) severely restricts the application of water splitting. In this paper, a free-standing serrated Ni-WO3 electrode for OER was synthesized by a simple in-situ etching method using (NH4)2SO4 as etchant. The effect of etchant on structures of Ni-WO3 were studied carefully, indicating that the NH4+ and SO42- have a synergistic effect on the unique structure. The serrated Ni-WO3-3 (where 3 is the mass of (NH4)2SO4) dramatically enhance OER performance, an over-potential of only 265 mV at 10 mA cm−2 as compared with that 365 mV of serrated-free Ni-WO3. Interestingly, the structure and composition of the serrated Ni-WO3 electrode undergoes a self-reconstruction process during OER, the finally catalyst is interconnected by low crystallinity nickel oxy-hydroxide nanoparticles. This work mainly explores the influence of etching agent type, usage and reaction time on the morphology and properties of materials, and the reconstruction phenomenon in OER pre-catalyst was confirmed.