Oxygen vacancy in CoO/reduced graphene oxide composite for enhancing long-term effectiveness of photocatalytic CO2 reduction via mediating exciton

Photocatalytic reduction of carbon dioxide (CO₂) has been expected to be an effective way to reduce carbon emissions. Designing photocatalytic materials with long-term effectiveness is the key of photocatalytic technology. In this work, CoO nanoparticles loaded on the surface of reduced graphene oxide (rGO) membranes on silicon substrate were in-situ fabricated by one-step method. The resulting materials can convert CO₂ into carbon monoxide (CO) up to 70 h at a steady rate of ∼185 ± 30 µmol g⁻¹ h⁻¹ with a selectivity of nearly 100%. This material system contained rich oxygen vacancies and generated new oxygen vacancies during the photocatalytic process. Oxygen vacancies mediate the interactions with excitons: (i) promoting the dissociation of free excitons; (ii) leading to form bound excitons under the coupling effect with phonons, inhibiting the recombination of photogenerated electrons and holes as well as enhancing the long-term effectiveness of photocatalytic CO₂ reduction. We hope this work can provide valuable insights for the design and optimization of photocatalytic materials.