Synergistically boosting highly selective CO2–to–CO photoreduction over BiOCl nanosheets via in-situ formation of surface defects and non-precious metal nanoparticles

Hollow hierarchical BiOCl (BOC) assembled by nanosheets with highly exposed (001) facet is synthesized via a gas-bubble-template strategy. The as-synthesized BOC is further modified by thermal treatment in N2 to in-situ introduce oxygen vacancies (OVs) and metallic bismuth (Bi0) nanoparticles from the BOC lattice (Bi0/OVs-BOC). Thermal treatment in N2 enables an intimate contact between OVs-BOC and Bi0 nanoparticles, which is conducive to the transfer of photogenerated charge carriers. In CO2 photoreduction test, the Bi0/OVs-BOCs exhibit almost 100 % selectivity towards CO, and some of the samples also have a significant increase in yield. For instance, BOC-250 shows about 24.82 μmol∙g–1 h–1 CO2-to−CO photoreduction efficiency which is nearly four times higher than that of the BOC with high stability. It is found that suitable energy band structure and desirable intrinsic carrier mobility account for the substantial enhancement of CO2-to−CO photoreduction activity due to the in-situ introduction of OVs and Bi0 nanoparticles. Density functional theory (DFT) calculations unveil that the decreased reaction energy, the weakened adsorption energy for CO, and suitable adsorption energy for H and OH of Bi0/OVs-BOC lead to high selectivity. This work sheds light on the synergistic effect of in-situ formed OVs and metal nanoparticles on enhancing the photocatalytic activity and selectivity of solar energy materials.