Photo-chemical conversion of CO2 into solar fuels by photocatalysts has attracted significant attention. However, poor reaction efficiency remains a huge obstacle. Deep insight into the reaction mechanism of CO2, especially the active site of photocatalyst could provide scientific basis for the development of more efficient photocatalyst. The high inertness of CO2 and the multi-electron reduction feature on a photocatalyst determine high complexity of the reaction for the study. Here, pure Bismuth oxyhalides (BiOX, where X = F, CI, Br, I) with the layered structure, which were synthesized by both hydrothermal method and chemical precipitation method, were selected as model photocatalysts. The photocatalytic behaviors of the samples were evaluated by the CO2 reduction with H2O without the additional photosensitizer and sacrificial agent. The as-prepared BiOBr was observed to exhibit the best CO2 photoreduction performance under the simulated sunlight. The evolution rates of CO and CH4 are 21.6 μmol g−1 h−1 and 1.2 μmol g−1 h−1, respectively. The effects of water dosage, light intensity and irradiation time on the efficiency of CO2 photoreduction were investigated systematically. Interestingly, the reduction selectivity of CO2 to CO almost reaches 100% in the case of high light intensity. By combination with isotopic tracing method, electron spin-paramagnetic resonance (ESR), in-situ Fourier transform infrared (FTIR) characterization, positron annihilation lifetime (PAL) spectra, and Density functional theory (DFT) calculation, the oxygen vacancy mediated mechanism of photoreduction CO2 was suggested for BiOX. This work provides new information and insights to deepen the understanding for defect photocatalysis on CO2 reduction of semiconductor.

Photocatalytic reduction of CO2 on BiOX： Effect of halogen element type and surface oxygen vacancy mediated mechanism

Recent development in band engineering of binary semiconductor materials for solar driven photocatalytic hydrogen production

Single-Atom Pt loaded Zinc Vacancies ZnO-ZnS Induced type-V Electron Transport for Efficiency Photocatalytic H2 Evolution

Harvesting solar energy for energy and environmental applications is an ever-fascinating field of research. Although semiconductor photocatalysis is the potential tool for recalcitrant degradation, it still suffers from rapid recombination, inability to utilize visible light, and lower photocatalytic performance. Recently, the Z-scheme photocatalysts are becoming research hotspots for their strong redox ability, charge carrier separation, and ability to exploit visible light. This review provides insights into the fundamental mechanism, synthesis strategies, and characterization techniques of Z-scheme photocatalysts. The recent advancements in their applications in visible-light-driven pollutants degradation are also reviewed.

Z-scheme photocatalysts for visible-light-driven pollutants degradation: A review on recent advancements

Enhanced visible-light-induced photocatalytic degradation of tetracycline using BiOI/MIL-125(Ti) composite photocatalyst

All-solid-state Z-scheme Pt/ZnS-ZnO heterostructure sheets for photocatalytic simultaneous evolution of H2 and O2

Bismuth iodide oxide (BiOI) as visible-light photocatalysts are widely applied to photodegradation reactions. Although surface atom tailoring has been actively used to modify electronic structures for improving photocatalytic activity, the functional groups used in improving surface reaction sites and surface band structure of BiOI has been largely overlooked. Here we report a new surface engineering strategy using deliberately selected organic solvents to tailor the surface structures and photocatalytic property of the BiOI nanosheets. Interestingly, the BiOI nanosheets modified by glycerol which contains abundant hydroxyl groups exhibit a more positive surface valance band maximum than that of BiOI synthesized in water. Consequently, the oxidation ability of photogenerated holes from hydroxyl-regulated BiOI is substantially improved, evident by the highly effective degradation of phenol and organic dyes under visible light, and a photoelectrochemical water splitting activity. The new findings provide a new strategy in tailoring surface atom structure by specific functional groups towards highly efficient photocatalysts.

Hydroxyl-regulated BiOI nanosheets with a highly positive valence band maximum for improved visible-light photocatalytic performance

Hexavalent chromium Cr(VI) is a well-known heavy metal widely existing in wastewater due to various anthropogenic activities. Cr(VI) ions are not biodegradable and tend to be toxic both in flora and fauna. Therefore, effective removal of Cr(VI) has become a very important procedure for treating Cr(VI)-containing wastewater. Here, we developed a facile strategy for constructing ZnO sheets with defective zeolite imidazolate frameworks-8 (ZIF-8) to form visible-light-driven ZIF-8@ZnO composite for efficient photoreduction of Cr(VI). It is widely accepted that both neat ZnO and ZIF-8 show no visible-light photocatalytic activity. However, our study demonstrates that a wide visible-light absorption band is observed in defective ZIF-8@ZnO after introducing self-defects in ZIF-8. Moreover, this strategy of visible-light Zn-based composite photocatalysts can also be used to design other photocatalytic materials for heavy metal treatment.

Visible-light-driven zeolite imidazolate frameworks-8@ZnO composite for heavy metal treatment

Fructose-regulated ZnO single-crystal nanosheets with oxygen vacancies for photodegradation of high concentration pollutants and photocatalytic hydrogen evolution

Yang Zhang

Papers

All-solid-state Z-scheme Pt/ZnS-ZnO heterostructure sheets for photocatalytic simultaneous evolution of H2 and O2

Hydroxyl-regulated BiOI nanosheets with a highly positive valence band maximum for improved visible-light photocatalytic performance

Visible-light-driven zeolite imidazolate frameworks-8@ZnO composite for heavy metal treatment

Fructose-regulated ZnO single-crystal nanosheets with oxygen vacancies for photodegradation of high concentration pollutants and photocatalytic hydrogen evolution

Meso-erythritol-regulated BiOBr nanosheets with surface hydroxyl imprinting sites for considerably improved photocatalytic capability