Molecular oxygen activation: Innovative techniques for environmental remediation

Molecular oxygen as a green, non-toxic, and inexpensive oxidant has displayed numerous advantages compared with other oxidants for more sustainable and environmentally benign pollutant degradation. Molecular oxygen activation stands as a groundbreaking approach in advanced oxidation processes, offering efficient environmental remediation with minimal environmental impact with the production of high-oxidation reactive oxygen species (ROS). The adaptability and energy efficiency of molecular oxygen activation significantly contribute to the progression of sustainable water remediation technologies. This review meticulously explores the principles and mechanisms of molecular oxygen activation, shedding light on the diverse ROS production pathways. Subsequently, this review comprehensively details contemporary activation approaches, including photocatalytic activation, electrocatalytic activation, piezoelectric activation, and photothermal activation, explicating their distinct activation mechanisms. Additionally, it delves into the promising applications of molecular oxygen activation in the degradation of water pollutants, primary air pollutants, and volatile organic compounds, providing an in-depth analysis of the associated degradation pathways and mechanisms. Moreover, this review also addresses the imminent challenges and emerging opportunities in environmental remediation. It is envisioned that this comprehensive analysis will spur ongoing exploration and innovation in the use of molecular oxygen activation for environmental remediation and beyond.

Surface and interface engineering of BiOCl nanomaterials and their photocatalytic applications

BiOCl materials have received much attention because of their unique optical and electrical properties. Still, their unsatisfactory catalytic performance has been troubling researchers, limiting the application of BiOCl-based photocatalysts. Therefore, many researchers have studied the adjustment of BiOCl-based materials to enhance photocatalytic efficiency. This review focuses on surface and interface engineering strategies for boosting the photocatalytic performance of BiOCl-based nanomaterials, including forming oxygen vacancy defects, constructing metal/BiOCl, and the fabrication of semiconductor/BiOCl nanocomposites. The photocatalytic applications of the above composites are also concluded in photodegradation of aqueous pollutants, photocatalytic NO removal, photo-induced H2 production, and CO2 reduction. Special emphasis has been given to the modification methods of BiOCl and photocatalytic mechanisms to provide a more detailed understanding for researchers in the fields of energy conversion and materials sciences.

Rational Atom Substitution to Obtain Efficient, Lead-Free Photocatalytic Perovskites Assisted by Machine Learning and DFT Calculations

Inorganic lead-free halide perovskites, devoid of toxic or rare elements, have garnered considerable attention as photocatalysts for pollution control, CO2 reduction and hydrogen production. In the extensive perovskite design space, factors like substitution or doping level profoundly impact their performance. To address this complexity, a synergistic combination of machine learning models and theoretical calculations were used to efficiently screen substitution elements that enhanced the photoactivity of substituted Cs2 AgBiBr6 perovskites. Machine learning models determined the importance of d10 orbitals, highlighting how substituent electron configuration affects electronic structure of Cs2 AgBiBr6 . Conspicuously, d10 -configured Zn2+ boosted the photoactivity of Cs2 AgBiBr6 . Experimental verification validated these model results, revealing a 13-fold increase in photocatalytic toluene conversion compared to the unsubstituted counterpart. This enhancement resulted from the small charge carrier effective mass, as well as the creation of shallow trap states, shifting the conduction band minimum, introducing electron-deficient Br, and altering the distance between the B-site cations d band centre and the halide anions p band centre, a parameter tuneable through d10 configuration substituents. This study exemplifies the application of computational modelling in photocatalyst design and elucidating structure-property relationships. It underscores the potential of synergistic integration of calculations, modelling, and experimental analysis across various applications.

3D structured TiO2-based aerogel photocatalyst for the high-efficiency degradation of toluene gas

A 3D TiO2-based aerogel is prepared that improves the mass-transfer efficiency of the gas–solid reaction for the high-efficiency degradation of toluene gas.

pH-Controlled assembly of [ZnW12O40]6--based hybrids from a 0D dimer to a 2D network: synthesis, crystal structure, and photocatalytic performance in transformation of toluene into benzaldehyde

Polyoxometalate-based organic-inorganic hybrids have attracted considerable attention due to their fascinating structures and wide application prospects. In this work, using the same building blocks, ligands and metal ions (ZnW₁₂O₄₀^6-(ZnW₁₂), 2,2'-bipyridine (2,2'-bipy), and Cu²⁺), we synthesized three new POM-based hybrids by controlling the pH values of the reaction systems. These three compounds {(Zn_0.6(H₂)_0.4W₁₂O₄₀)[Cu(2,2'-bipy)(H₂O)][Cu(2,2'-bipy)(H₂O)₂][Cu(2,2'-bipy)(H₂O)₃]}₂·6H₂O (1), (Me₄N)₂{ZnW₁₂O₄₀[Cu(2,2'-bipy)(H₂O)][Cu(2,2'-bipy)(H₂O)₃]}·5H₂O (2), and {(Zn_0.5(H₂)_0.5W₁₂O₄₀)[Cu(2,2'-bipy)][Cu(2,2'-bipy)(H₂O)][Cu(2,2'-bipy)(H₂O)₂]}·5H₂O (3) have been structurally characterized by single-crystal X-ray diffraction. Compound 1 appears as a dimeric cluster structure, while compounds 2 and 3 appear as a 1D chain structure and a 2D network, respectively. The semiconducting properties of compounds 1-3 are different, which was demonstrated by band gap (E_g) and photocurrent response measurements. Compound 3 can efficiently catalyze the photooxidation of toluene to benzaldehyde with high selectivity using molecular oxygen as the oxidant component. Moreover, compound 3 was recycled and reused three times without significant degradation in conversion and selectivity. In addition, the mechanism of the photocatalytic reaction was also investigated.