Room-temperature controllable synthesis of Bi5O7I nanostrips for improved photocatalytic activity

Strategies for improving the photocatalytic performance of metal-organic frameworks for CO2 reduction: A review

Photocatalytic CO₂ reduction is an appealing strategy for mitigating the environmental effects of greenhouse gases while simultaneously producing valuable carbon-neutral fuels. Numerous attempts have been made to produce effective and efficient photocatalysts for CO₂ reduction. In contrast, the selection of competitive catalysts continues to be a substantial hindrance and a considerable difficulty in the development of photocatalytic CO₂ reduction. It is vital to emphasize different techniques for building effective photocatalysts to improve CO₂ reduction performance in order to achieve a long-term sustainability. Metal-organic frameworks (MOFs) are recently emerging as a new type of photocatalysts for CO₂ reduction due to their excellent CO₂ adsorption capability and unique structural characteristics. This review examines the most recent breakthroughs in various techniques for modifying MOFs in order to improve their efficiency of photocatalytic CO₂ reduction. The advantages of MOFs using as photocatalysts are summarized, followed by different methods for enhancing their effectiveness for photocatalytic CO₂ reduction via partial ion exchange of metal clusters, design of bimetal clusters, the modification of organic linkers, and the embedding of metal complexes. For integrating MOFs with semiconductors, metallic nanoparticles (NPs), and other materials, a number of different approaches have been also reviewed. The final section of this review discusses the existing challenges and future prospects of MOFs as photocatalysts for CO₂ reduction. Hopefully, this review can stimulate intensive research on the rational design and development of more effective MOF-based photocatalysts for visible-light driven CO₂ conversion.

Z-Scheme Heterojunction of 3-Dimensional Hierarchical Bi3O4Cl/Bi5O7I for a Significant Enhancement in the Photocatalytic Degradation of Organic Pollutants (RhB and BPA)

In this study, we report the synthesis of a 3-dimensional (3D) hierarchical Bi3O4Cl/Bi5O7I (BOC/BOI) heterostructure for the photocatalytic degradation of Rhodamine-B (RhB) dye and colorless Bisphenol-A (BPA) pollutant under visible light. The heterostructure was prepared using in situ solvothermal and calcination methods. BOC/BOI exhibits a 3D hierarchical structure constructed with thin nano-platelets. The photocatalytic performance of the BOC/BOI photocatalyst demonstrated that the degradation efficiencies of RhB and BPA were 97% and 92% after light illumination within 90 and 30 min, respectively. In comparison, bare BOC and BOI efficiencies were only 20% and 10% for RhB dye, respectively, and 2.3% and 37% for BPA aqueous pollutants, respectively. Moreover, radical trapping measurements indicated that •O2− and •OH radicals played prominent roles in RhB and BPA degradation into mineralization. Analysis of band structures and photochemical redox reactions of BOC/BOI revealed a Z-scheme charge transfer between BOC and BOI by an internal electric field formed at the interface. Therefore, the highly improved photocatalytic performance of the BOC/BOI heterostructure is attributed to the synergetic effects of large surface area, high visible-light absorption, and the enhanced separation and transport of photo-excited electron–hole pairs induced by the hierarchical and Z-scheme heterojunction of the BOC/BOI.

Transformation of phase and heterojunction type by using HAc-adsorbed Bi(NO3)3 as a Bi source

Generally, preparing high-efficiency heterojunction photocatalysts via a facile room-temperature route is attractive from the perspective of energy and labor saving. Herein, by using dried and glacial acetic acid (HAc)-adsorbed bismuth nitrate, instead of Bi(NO₃)₃·5H₂O, as a Bi source, a β-Bi₂O₃/Bi₅O₇I heterojunction with well dispersed flowery hierarchical architecture was synthesized, which endows it with high surface area, open channels and good light harvest. More importantly, the change of the precursor achieved a successful transformation for both of phase and heterojunction type, i.e. from type-Ⅰ BiOI/[Bi₆O₅(OH)₃](NO₃)₅·3H₂O (labeled as BiOI/BBN) to Z-scheme β-Bi₂O₃/Bi₅O₇I heterojunction. Since both β-Bi₂O₃ and Bi₅O₇I are visible light responsive, β-Bi₂O₃/Bi₅O₇I exhibited improved visible-light photocatalytic activity for the degradation of tetracycline (TC) and malachite green (MG) with apparent reactant rate (k_app) values about 10 and 11 times higher than those of BiOI/BBN. Besides, the presence of more oxygen vacancies also contributed to the enhancement in photocatalytic performance.

Enhanced photocatalytic activity of Bi2WO6 with PVP addition for CO2 reduction into ethanol under visible light

The conversion of CO₂ into new carbon-based products, such as fuels and chemicals, is an attractive and promising means of mitigating global energy needs and minimizing environmental damage. Although bismuth tungstate (Bi₂WO₆) as a photocatalyst can promote CO₂ photoreduction, a systematic study for the development of a low-cost and efficient catalyst is needed. Thus, Bi₂WO₆ with different morphologies was successfully synthesized using the hydrothermal method. An experimental design was applied to investigate the effect of synthesis time and PVP (polyvinylpyrrolidone) concentration on catalyst photocatalytic activity. Crystal structures, morphologies, optical absorption, and surface charges of the catalysts were characterized by X-ray diffraction, scanning electron microscope, UV-vis diffuse-reflection spectroscopy, nitrogen adsorption, and zeta potential. All samples exhibited good performance for the photoreduction of CO₂ into ethanol, and both time and PVP concentration were significant in the ethanol yield. Changes in synthesis conditions induced differences in catalyst characteristics, such as morphology, crystallinity, and, predominantly, surface area. Furthermore, PVP addition improved photocatalytic efficiency by up to 258% compared with results without the surfactant. The best sample, W-8h-10%, presented a flower-like morphology and ethanol yield of 68.9 μmol g^-1 h^-1.