Rape straw biochar-assisted preparation of flower-like BiOCl with enriched oxygen vacancies for efficient photocatalytic CO2 reduction and pollutants degradation

Abstract

Utilizing photocatalytic technology to transform CO₂ into high added value chemical products has represented an effective strategy for alleviating the climate problems that have arisen due to excessive CO₂ emissions. As a typical bismuth-based photocatalyst, BiOCl has garnered widespread attention due to its unique layered structure and low toxicity. However, the low light utilization efficiency and the rapid recombination of e⁻/h⁺ pairs severely hinder the practical application of BiOCl. Introducing oxygen vacancies (OVs) into BiOCl has been demonstrated to be one of the effective strategies for enhancing the photocatalytic performance of BiOCl. However, introduction of OVs through a mild and cost-effective approach remains a significant challenge. In this work, we developed a strategy for introducing OVs on BiOCl, which indues the growth of BiOCl into flower-like spherical structures and introduction of abundant OVs through addition of rape straw biochar (RC) under hydrothermal conditions. The synergistic interaction of RC and OVs endows with BiOCl more active sites as well as higher photogenerated carriers (e⁻/h⁺) separation efficiency. When the mass ratio of RC to BiOCl is 0.5 % (RC-0.5), the sample demonstrates the best performance, conversion of CO₂ to CO on the sample is 4.0 μmol g⁻¹ h⁻¹, which is 3.08 times higher than that on the reference BiOCl. Additionally, versatility of the photocatalysts was further evaluated through photocatalytic degradation of rhodamine B (RhB) and perfluorooctanoic acid (PFOA). The degradation rate constant of RhB and PFOA on the RC-0.5 sample is 0.0642 min⁻¹ and 0.00566 min⁻¹, respectively, which is 2.26 times and 0.43 times higher than that on the reference BiOCl. Total organic carbon (TOC) experiments demonstrate that RhB can be effectively mineralized into CO₂, H₂O and small molecules on the photocatalyst. The main reactive species involved in the photocatalytic degradation process were investigated through active free radical trapping experiments and electron paramagnetic resonance (EPR). This work provides a viable strategy for the development of high-performance BiOCl photocatalysts for environmental applications.