Pt/TiO2-ZnO in a circuit Photo-electro-catalytically removed HCHO for outstanding indoor air purification

Challenges and Perspectives on Photocatalytic Membrane Reactors for Volatile Organic Compounds Degradation and Nitrogen Oxides Treatment

Air pollution is a pressing environmental and public health issue, with volatile organic compounds (VOCs) and nitrogen oxides (NO x ) being among the most hazardous airborne pollutants. Photocatalytic membrane reactors (PMRs) have emerged as a promising technology for air purification due to their ability to integrate photocatalytic degradation and membrane separation in a single system. This paper provides a comprehensive review of the advancements, challenges, and future prospects of PMR technology for VOC degradation and NO x treatment. Various photocatalytic membranes and their fabrication techniques, including material selection, structural modifications, and catalyst immobilization strategies, are critically analyzed. The study further explores different PMR configurations, operational parameters, and their efficiency in air treatment applications. A theoretical PMR test system is also presented to evaluate design optimization strategies. Despite its potential, challenges such as membrane fouling, catalyst deactivation, and scale-up limitations remain critical barriers to widespread adoption. Future trends focus on enhancing photocatalytic performance, developing cost-effective materials, and optimizing reactor designs to facilitate large-scale industrial applications of PMRs.

Research status of volatile organic compound (VOC) removal technology and prospect of new strategies: a review

As an important component of air pollution, the efficient removal of volatile organic compounds (VOCs) is one of the most important challenges in the world. VOCs are harmful to the environment and human health. This review systematically introduced the main VOC control technologies and research hotspots in recent years, and expanded the description of electrocatalytic oxidation technology and bimetallic catalytic removal technology. Based on a three-dimensional electrode reactor, the theoretical design of a VOC removal control technology using bimetallic three-dimensional particle electrode electrocatalytic oxidation was proposed for the first time. The future research focus of this method was analyzed, and the importance of in-depth exploration of the catalytic performance of particle electrodes and the system reaction mechanism was emphasized. This review provides a new idea for using clean and efficient methods to remove VOCs.

Thermal vacuum de-oxygen fabrication of new catalytic pigments: SiO2@TiO2-x amorphous photonic crystals for formaldehyde removal

Eliminating benzene and formaldehyde pollution is indispensable after the popularity of colorful home decoration in current society. The possibility and advantages of vividly colorful amorphous photonic crystals (APCs) as catalytic pigments were established. Biomimetic synthesis of APCs is an effective approach to obtaining angle-independent structural colors. Herein, we introduce oxygen vacancies through thermal vacuum de-oxygenation to synthesize SiO₂@TiO_2-x APCs for angle-independent structural colors and enhanced photocatalytic performance in one step. Core-shell nanospheres with controllable particle size were synthesized using a mixed-solvent method as the structural unit of APCs to prepare seven structural colors: red, orange, yellow, green, cyan, blue, and purple. The photocatalytic activity of in situ fabricated SiO₂@TiO_2-x APCs was conspicuously enhanced by thermal vacuum deoxidation. An amorphous layer formed on the TiO₂ nanocrystals provides TiO_2-x with excellent spectral response to visible light, transient photocurrent, and surface photovoltage up to 38.44 μA cm^-2 and 28.8 mV, respectively. Black TiO_2-x absorbs incoherent scattering, causing APCs to generate vividly angle-independent structural colors. The existence of oxygen vacancies in TiO_2-x promotes electron activation and a synergistic effect with the photonic local effect of APCs in improving the degradation of formaldehyde by catalytic pigments, effectively protecting the beautiful living environment of human beings.

A novel UV-assisted PEC-MFC system with CeO2/TiO2/ACF catalytic cathode for gas phase VOCs treatment

Emissions of volatile organic compounds (VOCs) air pollutants could worsen air quality and adversely affect human health, thus developing more efficient low-temperature VOCs removal techniques is desired. A novel continuous system integrating UV-assisted photo-electrochemical catalysis with microbial fuel cell (UV-assisted PEC-MFC) has been established for promoting removal of gaseous ethyl acetate or toluene and generating electricity simultaneously. In this system, CeO₂/TiO₂/ACF catalytic cathode is prepared and used for combination with bio-anode for accelerating cathodic reaction. This UV-assisted PEC-MFC system exhibits an excellent elimination capacity (EC) of ethyl acetate (∼0.39 g/m³, EC: ∼2.52 g/m³/h) or toluene (∼0.29 g/m³, EC: 1.89 g/m³/h) under close-circuit condition. Furthermore, an outstanding elimination capacity (EC: 28.04 g/m³/h) for high concentration toluene (∼4.10 g/m³) removal is obtained after toluene gas passes sequentially through the catalytic cathode then the bio-anode. This way of PEC degradation and biodegradation, avoids inhibition of exoelectrogens activity from toxicity of high concentration toluene. Simultaneously, the cell voltage of UV-assisted PEC-MFC system is stable at 0.11 V (vs. SCE) and 1.452×10^-4 kWh is generated from treatment of toluene gas stream in 6 h duration time. The possible mechanism of VOCs removal in this novel system has been proposed and discussed. This study provides new technical basis for treating gaseous pollutants via integrating photo-electrochemical catalysis with electricity generating microbial fuel cell for energy conversion.

Oxidation of gas phase ammonia via accelerated generation of radical species and synergy of photo electrochemical catalysis with persulfate activation by CuO-Co3O4 on cathode electrode

To enhance the efficiency of SO₄^- based advanced oxidation processes (AOPs) in synergy with photocatalysis in eliminating contaminants, heterogeneous CuO-Co₃O₄ catalysts were synthesized by a co-precipitation method and evaluated in oxidizing ammonia (NH₃). The removal of 96.1 % NH₃ at room temperature was achieved in persulfate/photo-electrochemical catalysis (PEC/PS). The factors influencing NH₃ removal include molar ratios of Cu/Co in CuO-Co₃O₄, external resistance and PS concentration. The activation of PS is affected by loading of metal oxides catalyst and its Cu/Co molar ratio (2 is optimal). On the catalyst surface, Co and Cu species were the primary reactive sites. The reaction mechanism involves the in-situ PS activation in synergy with PEC, accelerating the production of radical species, thereby enhancing ammonia oxidation and removal.

Efficient gas phase VOC removal and electricity generation in an integrated bio-photo-electro-catalytic reactor with bio-anode and TiO2 photo-electro-catalytic air cathode

An efficient and cost-effective bio-photo-electro-catalytic reactor (BPEC) was developed, it combined bio-anode with TiO₂ photo-electro-catalytic air cathode and could remove rapidly model gas phase VOC ethyl acetate (EA) and generate electricity simultaneously. This BPEC system exhibited a synergistic effect between the photo-electro-catalysis and microbial fuel cell (MFC) bio-electrochemical process. Calculated kinetic constant of the BPEC system (0.085 min^-1) was twice the sum of those of photocatalysis (only electrolyte in the anode, without microbes, 0.033 min^-1) and MFC (no photocatalysis, 0.010 min^-1) systems. Compared to BPEC with proton exchange membrane (PEM) separator (59.6 mW/cm²), the system with polyvinylidene fluoride (PVDF) membrane had a higher EA degradation rate and power generation (92.8 mW/cm²). A lower external resistance resulted in a faster EA degradation rate. This report provides a new platform for treating other kinds of gas pollutants via integrated bio-electrochemical and gas-solid photo-electro-catalytic reactions, with energy generation and conversions.