Excited Electron‐Rich Bi^(3–x)+ Sites: A Quantum Well‐Like Structure for Highly Promoted Selective Photocatalytic CO₂ Reduction Performance

Abstract

Most of the current research on the photocatalytic mechanism of semiconductors is still on the simulation and evaluation of ground‐state active sites. Insights into photogenerated electron transition paths and excited‐state active sites during photocatalysis are still insufficient. Herein, combining femtosecond time‐resolved transient absorption spectroscopy, in situ Fourier‐transform infrared spectroscopy, synchronous illumination X‐ray photoelectron spectroscopy, and theoretical calculation results rationally reveal that in complex bimetallic oxyhalides the ultrathin rich oxygen vacancies (ROV) PbBiO2Cl (PBOC) double unit cell (DUC) layers facilitate migration and separation of photogenerated electrons from the bulk to Bi sites near the surface oxygen vacancies (OVs), then form the excited electron‐rich Bi(3–x)+ sites like quantum well structure. The excited Bi(3–x)+ sites act as wells for photogenerated electrons leading to lower energy barrier in the rate determining step for the formation of *CO from *COOH intermediate. Without photosensitizers and sacrificial agents, ROV DUC PBOC exhibit high CO generation rate (16.02 µmol h–1 g–1) that is 18 times higher than that of bulk PBOC. In situ characterization combined with theoretical calculation provides effective insight into the photocatalytic mechanism of photoexcited semiconductor materials.

Defect-Engineered Bi24O31Cl10 Nanosheets for Photocatalytic CO2 Reduction to CO

“…Each peak was deconvoluted into three peaks, respectively. The binding energies of O 1s core levels at 529.1, 530.5, and 531.7 eV were respectively assigned to the oxygen atom bound to the metal bismuth, the oxygen atoms located in the vicinity of an oxygen defect, and the surface hydroxyl groups . Apparently, contrast to the bulk Bi 24 O 31 Cl 10 , the peak area ratio originated from the oxygen vacancy in Bi 24 O 31 Cl 10 -OV greatly rose accompanying the decreased area ratio of lattice oxygen, further attesting that more oxygen vacancies have been created via constructing the ultrathin nanosheet structure.…”

“…Furthermore, the decreased band intensity at 2337 cm –1 demonstrated the depletion of the adsorption of CO 2 molecules on the surface of the Bi 24 O 31 Cl 10 -OV sample during the photocatalytic reduction process, revealing that the carbon source of the product CO indeed originated from CO 2 . It is worth noting that the gradually increased intensity at 1568 cm –1 with the prolonged light irradiation time was assigned to the typical COOH* intermediate, a critical intermediate for the formation of the CO product from CO 2 reduction. ,,, In addition, CO temperature-programmed desorption (CO-TPD) measurements were conducted to observe the CO desorption behavior on the surface of the as-prepared samples. As can be seen in Figure f, the lower desorption temperature of Bi 24 O 31 Cl 10 -OV reveals the weaker force between the final product CO and Bi 24 O 31 Cl 10 -OV, suggesting that *CO can be easily removed from the surface of the Bi 24 O 31 Cl 10 -OV material.…”

“…Converting CO 2 molecule into valuable chemical fuels or feedstock has great significance for the sustainable economic and social development. − Recently, photocatalytic technology is deemed as an exceedingly promising technique in the research field of energy conversion and environment restoration. − However, restricted by the extremely high dissociation energy of the C–O bond in a CO 2 molecule (750 kJ mol –1 ), the conversion and selectivity of the photocatalytic CO 2 reduction reaction are still unsatisfactory . Seeking a constructive strategy to strengthen the CO 2 adsorption and activation capacity on the surface of the semiconductors has a fundamental significance in boosting the CO 2 photoreduction activity.…”

Synthesis of Bi25FeO40 Nanoparticles with Oxygen Vacancies via Ball Milling for Fenton Oxidation of Tetracycline Hydrochloride and Reduction of Cr(VI)

“…It may cause a variety of hazards and reactions to the human body, such as tissue cell damage, digestive system damage, bone growth retardation, liver and kidney toxicity, etc. Many technologies have been proposed to achieve harmless treatment of Cr­(VI) and tetracyclines, such as electrocatalysis, biodegradation, photocatalysis, − etc. Furthermore, the Fenton reaction has increasingly become an irreplaceable process for wastewater treatment, due to its generation of highly reactive ·OH (2.8 V).…”

Modified UiO-66-Br Microphotocatalyst with High Electron Mobility Enhances Tetracycline Degradation

“…To improve the high electron transport performance of UiO-66 through functional group modification and given the excellent light response and electron–hole separation ability of BiOBr, , this paper proposed a method that took the bromine functional group of UiO-66-Br as the bromine source, directly generating BiOBr at the ligand position through a solvothermal reaction. Through a series of characterizations, the microstructure, morphology, phase, and optical properties of the samples were studied.…”