Novel Au/La-Bi₅O₇I Microspheres with Efficient Visible-Light Photocatalytic Activity for NO Removal: Synergistic Effect of Au Nanoparticles, La Doping, and Oxygen Vacancy

Abstract

Sphere-like Bi 5 O 7 I (BOI) doped with La (L-BOI) samples were prepared by a solvothermal method followed by calcination at 450 °C for 2 h. Au nanoparticles were loaded on 6% La-doped Bi 5 O 7 I (2%A− 6%L-BOI) microspheres by a room-temperature chemical reduction method. The UV−vis absorption spectra show that the L-BOI and 2%A− 6%L-BOI samples have a strong visible-light absorption in comparison with the pure BOI. The electron paramagnetic resonance results indicate that the number of oxygen vacancies in L-BOI samples is increased with an increasing amount of the La dopant. The band structure of the prepared photocatalysts is investigated by confirming the positions of the valence band (VB) measured by XPS-VB and the Fermi level computed by density functional theory, respectively. NO is selected as a target gaseous pollutant to confirm the influence of La doping and the plasmonic effect of Au nanoparticles on the photocatalytic activity of BOI microspheres. The 2%A−6%L-BOI sample exhibits an enhanced photocatalytic performance compared to BOI, L-BOI, and A-BOI photocatalysts under visible-light irradiation. Interestingly, the 2%A−6%L-BOI sample also can reduce the amount of intermediate NO 2 during the NO removal process. The enhanced photocatalytic efficiency of the 2%A−6%L-BOI photocatalyst is profited from the synergy of La-ion doping, oxygen vacancy, and the surface plasmon resonance effect of Au nanoparticles. Based on the results of trapping experiments and electron spin resonance spectroscopy tests, h + , e − , and • O 2 − were involved in the NO oxidative removal.

Constructing the Pd/PdO/β‐Bi2O3 microspheres with enhanced photocatalytic activity for Bisphenol A degradation and NO removal

“…(d)). However, the E VB of β‐Bi 2 O 3 (1.80 V) is more negative than the standard redox potential of OH − /•OH (2.40 V) . Therefore, the photogenerated h + in the E VB of β‐Bi 2 O 3 could not form active species •OH from H 2 O.…”

“…Environmental pollution has gained widespread attention at a global scale in today's society . In recent years, owing to the excellent characteristics of bismuth oxide (Bi 2 O 3 ), including safety, non‐toxicity, etc., the Bi 2 O 3 ‐based materials stand out from a large number of photocatalytic materials .…”

“…First, the OVs can form a doping level to improve light utilization and trap photogenerated e − to restrict the recombination of photogenerated e − / h + pairs, which can promote the transfer efficiency of charge carriers from photocatalytic materials . Moreover, the OVs on the surface is an ideal active site for a strong chemisorption of oxygen (O 2 ) molecules, thereby activating further O 2 to produce reactive superoxide radical (•O 2 − ) species and transforming to hydroxyl radical (•OH) species . These radicals can directly degrade pollutants that are adsorbed on the photocatalyst surface.…”

Inside‐and‐Out Semiconductor Engineering for CO2 Photoreduction: From Recent Advances to New Trends

“…Doping is always accompanied by the presence of vacancy defects in the crystal structure, which is due to the imbalance of charge or coordination in bulk structure. [ 275–277 ] The proper balance between doping and vacancies can extend visible‐light absorption, reduce the charge recombination, and maintain the adsorption of CO 2 , thus contributing to the prominent performance for CO 2 photoreduction. On the contrary, excessive doping amount will throw off this balance and does not usually guarantee an increase in photocatalytic activities.…”

Flower-like Bi0/CeO2−δ plasmonic photocatalysts with enhanced visible-light-induced photocatalytic activity for NO removal

“…Semiconductor-based photocatalytic oxidation technology has recently drawn much attention in NO removal owing to its high efficiency, less energy consumption, and eco-friendliness nature [3]. Much ef-forts have been done to explore various photocatalysts with excellent photocatalytic activities, such as TiO 2 [4], Bi 5 O 7 I [5], g-C 3 N 4 [6], etc. Among them, CeO 2 , a promising metal oxide semiconductor, has been extensively applied in various applications, including photocatalysis [7], gas detection [8], and pharmaceutics [9].…”