Construction of Z-scheme Bi2O3/CeO2 heterojunction for enhanced photocatalytic capacity of TiO2 NTs

Thermal decomposition synthesis of CuO on TiO2 NTs as promising photocatalysts for effective photoelectrocatalytic hydrogen evolution and pollutant removal

The preparation strategy is the important factor to obtain the effective photocatalyst, and the thermal decomposition could be used to prepare photocatalysts with high crystallinity and photoactivity. In this paper, thermal decomposition method was used to deposit CuO nanoparticles on TiO2 nanotube arrays (TiO2 NTs), and the TiO2 NTs/CuO exhibited remarkably high visible light absorption and photoelectrocatalytic performances toward dye degradation and Cr(VI) reduction. The potential degradation pathway and toxicities of rhodamine B (RhB) dyes and intermediates were investigated. Moreover, the high photoelectric conversion with visible light photocurrent of 25.94 μA/cm2 and interface photovoltage of -0.12 V was produced, and the visible light-induced photoelectrocatalytic water splitting performance was outstanding. The mechanisms of hybrid photocatalyst preparation and photocatalytic progress were analyzed, and the p-n heterojunction was the decisive factor of the excellent photocatalytic property. The preparation strategy of TiO2 NTs/CuO provides the reference and guidance for the effective photocatalysts used in industrial waste water remediation and new energy generation.

Photocatalytic Synergy Between α-Bi2O3 Nanosphere and Spindle MIL-88A for Gas-Phase CO2 Reduction

Visible light-active photocatalysts play a crucial role in gas-phase photocatalytic CO2 reduction, offering significant potential for sustainable energy conversion. Herein, we present the synthesis of spindle-shaped Iron (Fe)-based metal-organic framework (MOF) MIL-88 A, coupled with distinct α-Bi2O3 nanospheres. The α-Bi2O3/MIL88A heterostructure is formed by interacting opposite surface charges, enhancing visible-light absorption and efficient interfacial charge-carrier separation. Such low-cost photocatalysts have a 1.75 eV band gap and demonstrate enhanced efficacy in converting CO2 to CO, CH4, and H2 in water without using any sacrificial agents or noble metals compared to pristine MIL88A. In addition, in-situ Electron Spin Resonance (ESR) analyses revealed that these unique catalysts combination promoted enhanced interfacial charge dynamics, creating efficient trapping sites for photogenerated carriers. Further, in-situ Diffuse Reflectance Infrared Fourier Transfer Spectroscopy (DRIFTS) investigation elucidates the plausible reaction mechanism and provides an effective methodology for catalyst screening for CO2 photoreduction. This study offers an effective approach for synthesizing the earth-abundant heterostructure from metal oxide and low-cost MOFs, enhancing photocatalytic activity for sustainable carbon dioxide conversion into invaluable chemicals.

A Simple One-Pot Method for the Synthesis of BiFeO3/Bi25FeO40 Heterojunction for High-Performance Photocatalytic Degradation Applications

This study presents a facile one-pot synthesis method to fabricate BiFeO3-Bi25FeO40-Bi2O3 heterojunction photocatalysts with controllable compositions and pure phases. Three different binary heterojunctions (BiFeO3/Bi25FeO40, BiFeO3/Bi2O3, and Bi25FeO40/Bi2O3) and a ternary BiFeO3/Bi25FeO40/Bi2O3 heterojunction were formed, all exhibiting significantly enhanced photocatalytic performance for the degradation of methylene blue (MB) and phenol under visible light irradiation, outperforming the individual compositions. Notably, the BiFeO3/Bi25FeO40 heterojunction achieved the highest degradation efficiency (93.68% and 83.3% for MB and phenol, respectively) as well as excellent stability. Impressively, the phenol degradation efficiency of BiFeO3/Bi25FeO40 was even over twice that of BiFeO3 and Bi25FeO40, and four times higher than that of Bi2O3. The enhanced photocatalytic activity of the BiFeO3/Bi25FeO40 heterojunction is primarily attributed to the advantageous S-scheme band alignments that facilitate efficient charge separation and enhance redox capabilities. While other heterojunctions also exhibited improved MB and phenol degradation efficiency, each unique combination of materials led to distinct electronic structures and diverse reaction mechanisms. The simplicity and scalability of the synthesis method, combined with the remarkable photocatalytic performance of these BiFeO3-Bi25FeO40-Bi2O3 heterojunction materials, position them as highly promising candidates for applications in environmental remediation and solar energy conversion.

SbSeI for high-efficient photocatalytic degradation of multiple pollutants

Photocatalytic degradation is an effective technology for degrading water pollution that plays a significant role in environmental remediation. Ternary 2D ternary V-VI-VIIA semiconductors are ideal candidates for photocatalytic degradation of pollutants due to effective light absorption and high charge carrier mobility. In this work, high-quality SbSeI crystals were prepared using the chemical vapor transport (CVT) method and their photocatalytic degradation performance for multiple pollutants was studied. SbSeI exhibits excellent photocatalytic performance in the degradation of potassium dichromate (Cr (VI)), rhodamine B (RhB), tetracycline hydrochloride (TC-HCl) and methyl orange (MO). More than 98% of Cr (VI) and RhB can be removed after irradiation with an Xe lamp for 10 min and 40 min, respectively. The capture experiments and electron spin resonance results indicated that ·O2- plays a major role in reducing Cr (VI), while h+ plays a primary role in the degradation of MO, RhB and TC-HCl. Interestingly, the degradation rate of Cr (VI) is 1.3 times higher than that of a single pollutant system, and the degradation rate of RhB is 1.6 times higher, due to the enhanced separation and utilization of holes and electrons. The results demonstrate that SbSeI is a potential photocatalytic degradation material.

Electron deficient Bi3+δ serves as N2 absorption sites and inhibits carriers recombination to enhance N2 photo-fixation in BiOBr/TiO2 S-scheme heterojunction

Efficient carriers separation and multiple nitrogen (N2) activation sites are essential for N2 photo-fixation. Here, we found that the BiOBr/TiO2 (BBTO) displayed an attractive reversible photochromism (white → grey) due to the generation of electron deficient Bi3+δ, which was produced by the hole trapping of Bi3+ under light irradiation. Interestingly, more Bi3+δ were detected in the BBTO heterojunction than in pure BiOBr, attributing that the hole trapping was promoted by the built-in electric field in the Step scheme (S-scheme) heterojunction. In the BBTO, the electron deficient Bi3+δ enhanced carriers separation and served as the reactive active site to adsorb more N2. Consequently, the BBTO possessed an excellent N2 photo-fixation activity (191 μmol gcat-1 h-1), which was 7.7 and 18 times higher than that of pure BiOBr (24.8 μmol gcat-1 h-1) and TiO2 (10.6 μmol gcat-1 h-1), respectively. Therefore, this work provides a new perspective for enhancing N2 photo-fixation by the electron deficient photocatalysts with S-scheme heterojunction.

Facile Synthesis of Ni-Doped ZnO Nanoparticles Using Cashew Gum: Investigation of the Structural, Optical, and Photocatalytic Properties

This work adopted a green synthesis route using cashew tree gum as a mediating agent to obtain Ni-doped ZnO nanoparticles through the sol-gel method. Structural analysis confirmed the formation of the hexagonal wurtzite phase and distortions in the crystal lattice due to the inclusion of Ni cations, which increased the average crystallite size from 61.9 nm to 81.6 nm. These distortions resulted in the growth of point defects in the structure, which influenced the samples' optical properties, causing slight reductions in the band gaps and significant increases in the Urbach energy. The fitting of the photoluminescence spectra confirmed an increase in the concentration of zinc vacancy defects (VZn) and monovacancies (Vo) as Zn cations were replaced by Ni cations in the ZnO structure. The percentage of VZn defects for the pure compound was 11%, increasing to 40% and 47% for the samples doped with 1% and 3% of Ni cations, respectively. In contrast, the highest percentage of VO defects is recorded for the material with the lowest Ni ions concentration, comprising about 60%. The influence of dopant concentration was also reflected in the photocatalytic performance. Among the samples tested, the Zn0.99Ni0.01O compound presented the best result in MB degradation, reaching an efficiency of 98.4%. Thus, the recovered material underwent reuse tests, revealing an efficiency of 98.2% in dye degradation, confirming the stability of the photocatalyst. Furthermore, the use of different inhibitors indicated that •OH radicals are the main ones involved in removing the pollutant. This work is valuable because it presents an ecological synthesis using cashew gum, a natural polysaccharide that has been little explored in the literature.