Oxygen vacancy-rich hierarchical BiOBr hollow microspheres with dramatic CO₂ photoreduction activity

Conversion of carbon dioxide into useful chemicals has attracted great attention. However, the significant bottlenecks facing in the field are the poor conversion efficiency of CO₂ and low selectivity of products. Herein, hierarchical BiOBr hollow microspheres are fabricated by a solvothermal method using ethylene glycol (EG) as solvent in presence of polyvinyl pyrrolidone (PVP). The hollow BiOBr microspheres prepared at 120 °C exhibit the best performance for CO₂ photoreduction. The evolution rates of product CO and CH₄ are up to 88.1 µmol g^-1h^-1 and 5.8 µmol g^-1h^-1, which are 8.8 times and 5.8 times higher than that of plate-like BiOBr respectively. The hollow microspheres possess larger specific area and generate multiple reflections of light in the cavity, thus enhancing the utilization efficiency of light. The modulated electronic structure by oxygen vacancy (OVs) is beneficial to the transfer of photogenerated electrons and holes. Especially, the enriched charge density of BiOBr by OVs is conductive to the adsorption and activation of CO₂, which could lower the overall activation energy barrier of CO₂ photoreduction_. In summary, the synergistic effect of the hollow structure with OVs plays a vital role in boosting the photoreduction of CO₂ for BiOBr. This work provides a new opportunity for designing the high efficiency catalyst by morphology engineering with defects at the atomic level for CO₂ photoreduction.