Ni-doping V2O5@NC nanoflowers for oxygen evolution in electrolyzed water

Abstract

The oxygen evolution reaction (OER), a half-process of water electrolysis, involves four electron transfer processes with a high energy barrier, leading to slow reaction kinetics. Developing stable and high-efficiency OER electrocatalysts remains a major challenge in field of water electrolysis. Here, a novel Ni-doping V₂O₅@NC nanoflower-like catalyst is synthesized for OER reaction. Specifically, Ni-V₂O₅@NC is obtained by incorporating Ni into V₂O₅ through a simply hydrothermal- carbonization process, using NH₄VO₃, Ni(NO₃)₂·6 H₂O and H₂C₂O₄·₂H₂O as raw materials. This approach can improve the OER activity and stability of V₂O₅. Ni-V₂O₅@NC presents the following advantages. Firstly, Ni-doping combined with nanoflower structure improves the reaction activity. Ni-doping generates more electrochemical active sites, facilitating the adsorption/desorption process of reaction intermediates and electron transfer, thereby enhancing catalytic activity. Besides, the nanoflower-like structure provides a relatively high specific surface area and more active sites to participate in the reaction, thus boosting the catalytic reactivity. Secondly, Ni with high conductivity and its doping into V₂O₅ causes structural and performance changes of material, reducing the charge transfer resistance and optimizing the conductive property. Meanwhile, the inherent N and C from hydrothermal reaction also increase material conductivity. Also, Ni doping inhibits the stacking of V₂O₅ lamellar structure while maintaining the catalyst’s activity, structural integrity and the improved stability. The electrochemical analysis results show Ni-V₂O₅@NC good electrochemical performance. Ni-60-V₂O₅@NC features a low overpotential (300 mV@10 mA cm⁻²) and a small Tafel slope (74.2 mV dec⁻¹) in OER. Additionally, the overpotential of Ni-60-V₂O₅@NC only increases by 3 mV after 1000 cycles stability tests.