Activating Co(OH) ₂ Active Sites by Coupled with V ₂ O ₅ to Boost Highly Efficient Oxygen Evolution Reaction

Abstract Electrocatalytic water splitting generated oxygen (O 2 ) and hydrogen (H 2 ) 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 Co 2+ in Co(OH) 2 is further oxidized to Co 3+ 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 V 2 O 5 nanoflowers (Co(OH) 2 /V 2 O 5 ) at room temperature. The V 5+ of V 2 O 5 can oxidize Co 2+ of Co(OH) 2 into Co 3+ , 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 /V 2 O 5 ) than that of pure Co(OH) 2 . Therefore, the hybrid Co(OH) 2 /V 2 O 5 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 .