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

• The self-supported serrated Ni-WO 3 on Ni foam was obtained by one step in-situ etching method. • The NH 4 + and SO 4 2- had synergistic effect on the unique structure. • The serrated Ni-WO 3 exhibits excellent OER activities with low over-potentials of 265 mV at 10 mA cm−2. The effect of etching agent type and reaction time on the morphology and properties of materials was studied in this paper and the reconstruction phenomenon in OER pre-catalyst was confirmed. The serrated Ni-WO 3 -3 has excellent OER performance with an over-potential of only 265 mV at 10 mA cm−2. The serrated Ni-WO 3 electrode undergoes a self-reconstruction of structure and material during OER to form nickel oxy(hydroxide) nanoparticles. [Display omitted] The slow kinetics of oxygen evolution reaction (OER) severely restricts the application of water splitting. In this paper, a free-standing serrated Ni-WO 3 electrode for OER was synthesized by a simple in-situ etching method using (NH 4) 2 SO 4 as etchant. The effect of etchant on structures of Ni-WO 3 were studied carefully, indicating that the NH 4 + and SO 4 2- have a synergistic effect on the unique structure. The serrated Ni-WO 3 -3 (where 3 is the mass of (NH 4) 2 SO 4) 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-WO 3. Interestingly, the structure and composition of the serrated Ni-WO 3 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. [ABSTRACT FROM AUTHOR]