Carbon capture, utilization, and storage play vital roles in reducing CO₂ emissions and mitigating climate change intensifies. The ocean, as a major carbon sink, presents unique opportunities for carbon sequestration and utilization. In our study, we focus on the harvest of solar energy to drive the photocatalytic conversion of carbon-sequestrated seawater into CO as a potential fuel, and HClO disinfectant for ballast water sterilization, thus contributing to both carbon reduction and environmental sustainability.
We successfully synthesized nitrogen-doped BiOCl atomic layers, which efficiently split carbon-sequestrated natural seawater into stoichiometric CO and hypochlorous acid (HClO) under visible light. With selectivities greater than 90%, this system achieved CO production at a rate of 92.8 µmol·g⁻¹·h⁻¹ and HClO generation at 83.2 µmol·g⁻¹·h⁻¹. The nitrogen doping on the exposed BiOCl {001} facet enriched photoelectrons, facilitating CO₂-to-CO reduction, while photoholes on the lateral facets selectively oxidized chloride ions (Cl⁻) into HClO. Additionally, the sequestrated CO₂ maintained the seawater pH at 4.2, preventing the precipitation of alkaline earth cations, which can deactivate the photocatalyst. Importantly, the produced HClO demonstrates practical application for sterilizing ballast water in ocean-going ships, offering a green and efficient method for onsite disinfection. The dual benefits of our research contribute to the effective utilization of the ocean’s natural carbon sink capabilities, thus present a promising direction for mitigating greenhouse gas emissions while providing value-added chemical products.

CO2 reduction,photocatalysis,seawater split,ballast water