Directed Surface Reconstruction of Fe Modified Co₂VO₄ Spinel Oxides for Water Oxidation Catalysts Experiencing Self‐Terminating Surface Deterioration

Abstract Affordable highly efficient catalysts for electrochemical oxygen evolution reaction (OER) play pivotal roles in green hydrogen production via water electrolysis. Regarding the non‐noble metal‐based electrocatalysts, considerable efforts are made to decipher the cation leaching and surface reconstruction; yet, little attention is focused on correlating them with catalytical activity and stability. Herein, in situ reconstruction of Fe‐modified Co₂VO₄ precursor catalyst to form a highly active (Fe,V)‐doped CoOOH phase for OER is reported, during which partial leaching of V accelerates the surface reconstruction and the V reserved in the reconstructed CoOOH layer in the form of alkali‐resistant V₂O₃ serves for dynamic charge compensation and prevention of excessive loss of lattice oxygen and Co dissolution. Fe substitution facilitates Co pre‐oxidation and endows the catalysts with structural flexibility by elevating O 2p band level; hence, encouraging participation of lattice oxygen in OER. The optimized Co₂Fe_0.25V_0.75O₄ electrode can afford current densities of 10 and 500 mA cm⁻² at low overpotentials of 205 and 320 mV, respectively, with satisfactory stability over 600 h. By coupling with Pt/C cathode, the assembled alkaline electrolyzer can deliver 500 mA cm⁻² at a low cell voltage of 1.798 V, better than that of commercial RuO₂ (+) || Pt/C (−).