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 (−).