Bio-based mesoporous carbon-modified Co3O4 quantum dots as efficient electrocatalyst for freshwater, seawater and urea oxidation reaction

The combination of quantum dots (QDs) with carbon materials has garnered significant attention as electrocatalysts owing to their exceptional catalytic activity and robust thermodynamic stabilities. The present study utilizes bio-based mesoporous carbon as a carbon source to synthesize QDs carbon nanostructures (Co₃O₄/BMC_-400) through hydrothermal and carbonization methods. Due to the abundance of active sites and limited availability of Co, the size of Co particles is confined to the QDs level, ranging from 2 to 3 nm. The anodic oxidation reaction of the Co₃O₄/BMC_-400 was investigated in freshwater, seawater, and urea. The prepared Co₃O₄/BMC_-400 exhibits an oxygen evolution reaction overpotential of 235 mV at 10 mA cm⁻² in 1.0 M KOH. The catalytic activity is reduced as a result of the competitive oxidation and corrosion caused by chloride ions in seawater. For the urea oxidation reaction, Co₃O₄/BMC_-400 exhibits superior catalytic performance, requiring only a potential of 1.371 V at 10 mA cm⁻², while exhibiting remarkable long-term stability for up to 30 h. More significantly, in comparison to Co₃O₄ nanosheets and nanoparticles, QDs can effectively reduce the transport pathways of alkali metal ions, thereby affording an increased number of catalytic active sites while simultaneously enhancing stability and prolonging service life. These findings may facilitate further exploration of metal-QDs/carbon materials in a wide range of electrocatalytic application.