Surface Hydrogen Bond-Induced Oxygen Vacancies of TiO2 for Two-Electron Molecular Oxygen Activation and Efficient NO Oxidation

Dual-site Langmuir-Hinshelwood mechanism in ZnCr-LDH/NH2-UIO66 heterojunction for efficient photocatalytic NO oxidation

In this study, we developed a ZnCr-LDH/NH2-UIO66 heterojunction to enhance photocatalytic NO oxidation through a dual-site Langmuir-Hinshelwood (L-H) mechanism. Nitrogen oxides (NOₓ), including NO, are hazardous environmental contaminants linked to severe air pollution issues such as haze, acid rain, and photochemical smog. The composite catalyst addresses these challenges by synergistically activating NO and O2 under environmentally relevant conditions, including simulated solar light, ambient temperature, and NO concentrations of 1000 ppb typical of polluted urban areas. The MOF component (NH2-UIO66) selectively adsorbs NO, while the LDH component (ZnCr-LDH) efficiently activates O2 to generate reactive oxygen species (ROS). The built-in electric field (BIEF) optimizes charge separation, enabling 71.1 % NO removal efficiency with 97.8 % nitrate selectivity, effectively suppressing toxic NO2 byproduct formation. This work provides a sustainable strategy for mitigating hazardous NO emissions in air pollution control, bridging material design with environmental remediation.

Visible-light photocatalytic oxygen activation by oxygen vacancies-rich BiOI for enhanced removal of bisphenol A in water

Bisphenol A (BPA) is a persistent endocrine disruptor that poses high ecological and healthy risks. Photocatalytic oxygen (O2) activation has emerged as a promising technology for water decontamination, but its efficiency is often hindered by sluggish interfacial electron transfer between photocatalysts and O2 molecules. In this study, a Zn/S co-doping defect engineering strategy was developed to introduce oxygen vacancies (OVs) into BiOI for enhancing visible-light photocatalytic O2 activation and BPA removal. The OVs-rich BiOI with sub-band near the conduction band provided electron and reactant trapping sites that facilitated spatial separation of photogenerated electrons (e-) and holes (h+). The localized electrons at OVs reduced O2 via single-electron transfer to generate superoxide radicals (•O2-), which were further oxidized to singlet oxygen (1O2) by h+. Synergistic oxidation of 1O2 and h+ significantly enhanced BPA degradation, achieving approximately 90 % removal within 120 min. The reaction rate constant (0.01829 min-1) was nearly double that of pure BiOI (0.00948 min-1). Furthermore, the OVs-rich BiOI catalyst demonstrated excellent stability and reusability, maintaining >90 % BPA removal efficiency after five cycles of test. This study offers a new strategy for developing visible-light photocatalyst to remove recalcitrant emerging organic contaminants in water.

In situ growth of Cu0-modified oxynitride for optimized photocatalytic nitric oxide oxidation

Photocatalysis technology provides a promising and green strategy for the abatement of low-concentration NO pollutants in the ambient air. An earthworm-like oxynitride decorated with in situ grown Cu nanoparticles is synthesized through the ammonolysis of the CuO-doped ZnGa2O4 spinel. The optimized morphology promoted the exposure of active sites and expanded the reaction interface for efficient NO adsorption and photocatalytic conversion. The decoration of Cu0 and N3- doping enhanced the light absorption and imparted a tunable energy band structure. The strong interactions between Cu0 and the Ga1-xZnxN1-yOy interface maximize the utilizing photo-induced charge by facilitating the transfer and inhibiting the recombination of the charge carrier. The strong adsorption of H2O and NO on Cu0 and internal electric field of Cu0-Ga1-xZnxN1-yOy junction contribute to the high selectivity of NO. This study provides a new perspective on the design of visible-light-driven photocatalysts with Schottky junction for environmental remediation.

Zinc-doped C4N3/BiOBr S-scheme heterostructured hollow spheres for efficient photocatalytic degradation of tetracycline

Photocatalytic degradation of organic pollutants in water is of great significance to the sustainable development of the environment, but encounters limited efficiency when a single compound is used. Thus, there have been enormous efforts to find novel photocatalytic heterostructured composites with high performance. In this work, a novel S-scheme heterostructure is constructed with BiOBr and Zn2+ doped C4N3 (Zn-C4N3) by a solvothermal method for efficient photodegradation of tetracycline (TC), a residual antibiotic difficult to be removed from the aquatic environment. Thanks to Zn2+-doping induced improvement in chemical affinity between Zn-C4N3 and BiOBr, well-formed Zn-C4N3/BiOBr heterostructured hollow spheres are formed. This structure can efficiently suppress fast recombination of photogenerated electron-hole pairs to enhance the photocatalytic activity of BiOBr dramatically. At a room temperature of 25 °C and neutral pH 7, the catalyst can degrade a significant portion of TC pollutants within 30 min under visible light. Also, the Zn-C4N3/BiOBr heterostructure displays good stability after recycling experiments. Free radical capture experiments and ESR tests show that ˙O2- is the main active substance for photocatalytic degradation of TC. This study provides new insights for constructing heterostructures with an intimate interface between the two phases for photocatalytic applications.

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.