The development of efficient electrocatalysts for the oxygen evolution reaction (OER) is critical for advancing renewable energy technologies such as water electrolysis and carbon dioxide reduction. Despite significant progress, a persistent challenge remains in balancing high metal loading with ultrasmall particle size—two key factors that govern catalytic performance. While increasing metal loading enhances the number of active sites, it often leads to aggregation of metal species into larger nanoparticles due to high surface energy, thereby reducing overall efficiency. This work presents a bottom-up ligand-mediated strategy to synthesize ultrafine CoOx nanoclusters anchored on a nitrogen-containing carbon matrix (CoOx@Co-NC), successfully overcoming this trade-off. By utilizing oxalic acid as both an oxygen source and chelating agent during the polymerization of graphitic carbon nitride (g-C3N4), cobalt ions are uniformly dispersed within the precursor framework. Subsequent thermal treatment at 700 °C under nitrogen atmosphere results in the formation of highly dispersed CoOx nanoclusters (approximately 0.UBQ-3 NHS ester Autophagy 67 nm in size) and Co-N4 macrocycles, with a maximum cobalt loading reaching up to 20 wt.UPK3B Antibody supplier % without observable aggregation.PMID:35139420 The presence of both N and O atoms from the ligand framework stabilizes the cobalt species, preventing their migration and coalescence. Electrochemical evaluation reveals that the optimized 7.5% CoOx@Co-NC catalyst achieves an overpotential of only 353 mV at 10 mA/cm² and a Tafel slope of 40 mV/dec—superior to commercial RuO₂ (411 mV, 72 mV/dec). This enhanced activity stems from synergistic effects between the dual active centers: Co-N4 sites facilitate charge transfer and lower reaction barriers, while CoOx nanoclusters promote OH⁻ adsorption and interfacial mass transport. Moreover, the catalyst exhibits excellent long-term stability, maintaining its performance after 1000 cycles and 10 hours of chronoamperometry testing. X-ray photoelectron spectroscopy (XPS), HAADF-STEM, and EIS analyses confirm the electronic interaction between Co species and the carbon matrix, as well as low charge transfer resistance. These findings demonstrate that the ligand-mediated synthesis route enables precise control over metal dispersion and loading, offering a universal platform for designing high-performance, durable electrocatalysts for OER and other energy conversion applications.
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