The electrocatalytic urea oxidation reaction (UOR) has attracted substantial research interests during the past few years owing to its critical role in coupled electrochemical systems for energy conversion, for example,...

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In this work, Co-based nanocatalysts with variable degrees of sulfurization (DoS) were fabricated for the oxygen evolution reaction (OER).

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Main observation and conclusion Design and fabrication of earth‐abundant electrocatalysts for oxygen evolution reaction (OER) is essential in improving the overall efficiency of water electrolysis. In this work, we proposed a rapid and scalable synthesis route for fabricating Prussian blue analogue (PBA) nanocubes with tunable compositions and uniform particle size. With the structural benefits of abundant surface sites, facile charge transfer behavior and favorable Co2+‐to‐Co3+ pre‐oxidation reaction, fast generation and accumulation of the catalytically active Co3+ sites can be achieved for the CoCo PBA nanocubes, leading to remarkable OER activity with simultaneously achieved low overpotential, large anodic current density, small Tafel slope as well as outstanding intrinsic activity. Of note, by performing long‐term OER operation, the CoCo PBA nanocubes exhibit a remarkable 5.5‐folds performance enhancement, and obvious surface reconstruction and the accumulation of high‐valence Co species can be identified, proving the crucial role of pre‐oxidation process in boosting the OER catalysis. This work proposed a universal approach for the rapid, scalable and controllable fabrication of the PBA‐based materials, and the elucidation of the pre‐oxidation process in facilitating the OER catalysis may provide useful guidance for designing and optimizing advanced catalysts for energy‐related electro‐oxidation reactions in the future.