Electrochemical Synthesis of Cation Vacancy-Enriched Ultrathin Bimetallic Oxyhydroxide Nanoplatelets for Enhanced Water Oxidation

Metal cation vacancies, a kind of structural defect, are viewed as a promising strategy for regulating the electronic properties to enhance the catalytic activity. However, the effective introduction of cation vacancies into electrocatalysts still remains a challenge. Herein, we present and elucidate a facile "fast reduction and in situ phase transformation" strategy at room temperature to simultaneously introduce abundant metal cation vacancies (cobalt vacancies and iron vacancies) into Co0.5Fe0.5OOH electrocatalysts. The incorporation of the Fe element could tailor the micrometer-sized ultrathin CoOOH platelets into nanometer-sized ultrathin Co0.5Fe0.5OOH platelets, and the tailoring process is accompanied with the generation of numerous cation vacancies. The defect degree of CoOOH could be effectively tuned by the incorporation of Fe, resulting in more active sites and lower energy barrier, and thereby the intrinsic catalytic activity of electrocatalysts was further enhanced. Compared to CoOOH, the optimized nanometer-sized ultrathin Co0.5Fe0.5OOH platelets (Co0.5Fe0.5OOH-NSUPs) require a smaller overpotential of 220 mV at a current density of 20 mA cm–2, lower Tafel slope of 38.2 mV dec–1, and better long-term durability without obvious decay for more than 200 h at a high current density of 40 mA cm–2. The electrochemical performances are equal to or better than that of the reported first-class electrocatalysts. More importantly, this work provides new perspective for designing and fabricating efficient multimetal electrocatalysts in large scale.