Activating Co(OH)₂ Active Sites by Coupled with V₂O₅ to Boost Highly Efficient Oxygen Evolution Reaction

Abstract Electrocatalytic water splitting generated oxygen (O₂) and hydrogen (H₂) is a promising way to solve the energy crisis. Oxygen evolution reaction (OER) compared to hydrogen evolution reaction (HER) has slow kinetics hindering overall process. Recently, cobalt hydroxide (Co(OH)₂) with high activity and stability for OER has attracted more attention. During the OER process, the Co²⁺ in Co(OH)₂ is further oxidized to Co³⁺ and CoOOH species are true active sites. However, the low conductivity of Co(OH)₂ hinders its oxidization to CoOOH. In addition, spontaneous growth of Co(OH)₂ agglomerates easily during hydrothermal treatment, leading to decreased active sites. Herein, an efficient strategy is developed to construct highly dispersive Co(OH)₂ nanosheets vertically grown on V₂O₅ nanoflowers (Co(OH)₂/V₂O₅) at room temperature. The V⁵⁺ of V₂O₅ can oxidize Co²⁺ of Co(OH)₂ into Co³⁺, resulting in in situ formations of CoOOH species favorable to the OER process. In situ Raman also investigates that the OH^‐ species are inserted more easily into the interlayer of Co(OH)₂ of (Co(OH)₂/V₂O₅) than that of pure Co(OH)₂. Therefore, the hybrid Co(OH)₂/V₂O₅ exhibits low overpotentials of 320 and 370 mV at a current density of 10 and 50 mV cm^‐2, respectively, and a small Tafel slope of 68 mV dec^‐1.