Degradation Of Formaldehyde Research Articles

Catalytic activity of laundering durable fiber-based manganese dioxide catalyst targeting indoor formaldehyde

Fiber-based MnO2 nanocatalysts show high practical potential for their easy recovery. While significantly reducing specific surface area, catalytic performance, and poor laundering durability hinder their further applications for formaldehyde removal. Here, surface –OH and –COOH on PMIA were finely regulated by varying the plasma treatment durations. –OH plays as a reduction agent to facilitate the production of Mn3+ close to the PMIA surface and thus promote subsequent output of oxygen vacancy (OV). The plasma introduced and –OH oxidated –COOH acted together as multiple binding sites to bridge the MnO2 catalyst and PMIA fiber, which endows the MnO2@PMIA excellent laundering durability evidenced by the almost unchanged catalytic performance targeting formaldehyde even after 20 home laundering cycles. The mechanism of modulation of oxygen vacancy and specific surface area and water fastness by in situ –OH and –COOH on the relevant surfaces is proposed and confirmed by FTIR, XPS, SEM, and BET. MnO2@PMIA-6 demonstrated the highest catalytic activity for the degradation of formaldehyde, up to 95.43 % in 1 h at room temperature. The catalytic activity remained at 90.97 % with only 0.94 % loss of catalyst mass after 20 home laundering cycles.

Formulating the Li sites of Li-CoOx composites for achieving high-efficiency oxidation removal of formaldehyde over the Ag/Li-CoOx catalyst under ambient conditions

Oxide supported noble metals are extensively investigated for ambient formaldehyde oxidation, and the Ag-CoOx complex is one promising combination in terms of cost and activity. Further, we previously observed that cooperating Ag with Li + greatly boosted formaldehyde degradation on CoOx. Yet, there is still room for improvement in removal efficiency, mineralization capacity and resistance to severe conditions. These objectives could be realized via strategically formulating the Li+ sites of Li-CoOx composite in this sister study. Three samples with Li + ---Co3+—O2- connections (L-CO), spinel Li+ (LCO-S) and layered Li+ (LCO-L) were obtained at low (300 °C), moderate (500 °C) and high (700 °C) temperatures, respectively. The specific Li+ positions and componential interaction were demonstrated by Hyperspectral imaging (HSI), XRD, SEM, TEM, HAADF mapping, UV–vis DRS and XPS. Moreover, the effect of reactive oxygen exposure on catalytic oxidation of formaldehyde (330–350 mg/m3) was disclosed through CO-TPR and O2-TPD. Compared with the LCO-S and LCO-L, L-CO exhibited dominant formaldehyde degradation due to the larger content of surface oxygen. After Ag decoration, the Li+---Co3+—O2- connections uniquely caused a strong binding of Ag species with catalyst host, which boosted the amount of reactive oxygen and finally resulted in an even higher elimination of ∼73% (CO2 yield = ∼21%), 47% higher than that of the L-CO (CO2 yield = ∼6%). But in contrast, the Ag@LCO-S only achieved ∼53% removal (CO2 yield = ∼9%) and Ag modification was powerless in altering the inertness of LCO-L, demonstrating that the chemical environment of alkali metal is crucial to effectively tuning the catalyst activity. The advantage of Ag@L-CO in formaldehyde depollution was further reflected from its much better resistance to moisture and aromatic compound omnipresent in indoor air. For the first time, this study extended the understanding of the alkali-metal-promoted formaldehyde oxidation reaction to an in-depth level.

Low-cost and large-scale preparation of ultrafine TiO2@C hybrids for high-performance degradation of methyl orange and formaldehyde under visible light

Abstract Developing high-efficiency and low-cost visible light photocatalyst is a great challenge for degrading both air and liquid pollutants. Herein, we developed a large-scale preparation of ultrafine TiO2@C hybrid visible light photocatalyst for high-performance degradation of formaldehyde and methyl orange (MO) at low cost using the ultra-low temperature (<200°C) air calcination method. The as-designed TiO2@C hybrids are at the scale range of 2–5 nm and modified by ultrafine carbon layers enabling the strong physical adsorption and narrowing the corresponding band gap. Specifically, the photocatalytic performance of TiO2@C hybrids for formaldehyde and MO degradation was investigated both in the air and liquid pollutant. After optimization, the TiO2@C hybrid obtained at 175°C possesses relatively better photocatalytic degradation performance than other parallel control composites under visible light irradiation. The enhanced photodegradation ability of TiO2@C-175°C hybrid with visible light response attributes to novel hybrid structure with rich defect active sites and narrow band gap (2.51 eV), favoring dual functions of physical adsorption and chemical degradation. This ultra-low temperature air calcination approach can open a low-cost and scalable pathway to design TiO2@C hybrids for green environment.

Synergistic effects of multitype carbon doping and oxygen vacancies in TiO2/CNTs composite fabricated via nonthermal plasma for formaldehyde removal

Formaldehyde as one of the typical indoor pollutants has long been concerned as it can pose a threat to human health. TiO2/CNTs composite with oxygen vacancies and multitype carbon doping (C–TiO2/CNTs) was fabricated using nonthermal plasma for the photocatalytic degradation of formaldehyde. The maximum degradation rate of formaldehyde was 93% and 83% via the new catalyst (with 5% CNTs content) under solar and visible light, respectively. The characterization of the catalyst confirmed the in-situ multitype carbon doping and oxygen vacancies: interstitial carbon doping and oxygen vacancies could dramatically reduce the bandgap and contribute to the improved absorption capability of formaldehyde and electrons. Interfacial carbon doping in the form of C–O–Ti bonds provided a migration channel, whereby photogenerated electrons could efficiently transfer from CNTs to TiO2 and then quench the holes left in the VB of TiO2. Therefore, the multitype carbon doping and oxygen vacancies can expand the light response as well as promote the separation of photo-generated electron/hole pairs. EPR results and experiment section indicated that O2·− plays the most significant role in formaldehyde removal due to the reverse transfer of the electrons. This work advances the understanding of photo-degradation of TiO2/CNTs composite and provides a new route for the abatement of formaldehyde.

Performance analysis of a sorption heat storage-photocatalytic combined passive solar envelope for space heating and air purification

Efficient energy storage technology is a crucial step in achieving the broad deployment of solar energy. Salt hydrate-based sorption thermochemical energy storage (TCES), which relies on reversible gas-solid reactions, can provide an option for building energy conservation. In this article, a solar building envelope combining TCES and photocatalysis, which can fully utilize outdoor solar radiation and achieve dual-function of space heating and formaldehyde degradation is proposed. The thermal efficiency and the formaldehyde degradation effectiveness of the system under dynamic exterior conditions, as well as the influences of solar radiation, ambient temperature and wind speed, and channel width, are numerically studied. Results indicate the outlet air temperature and formaldehyde degradation rate surge first and then drop during charging, with the maximum outlet temperature of 47.9 °C at 14:30. The average ventilation volume rate of air, clean air delivery rate, and formaldehyde degradation rate are 38.8 m3/h, 29.4 m3/h, and 8.9425 μg/s, respectively. The discharging starts at 20:00 to upgrade the outlet temperature from 30 °C to around 40 °C, and the period can last for more than 10 h. The overall thermal efficiency of this sorbent wall is 66%. Increasing solar radiation and ambient temperature and lowering wind velocity can generally enhance the air purification effect and thermal efficiency; an interlayer width range of 6–8 cm is optimal to obtain better thermal and air purification performances. The results of this study demonstrate the significant potential of developing such a dual-function solar building envelope for air purification and space heating concurrently.

Nanostructured TiO2 co-modified with silver and bismuth for formaldehyde degradation under visible light

This study investigated the effect of Ag-Bi co-modified nanostructured TiO2 on photodegradation of gaseous formaldehyde (HCHO). The Ag/Bi-TiO2 materials were synthesized using the hydrothermal method with various concentrations of Ag (0–2 %). The synthesized materials were characterized using XRD, SEM, TEM, EDS, PL, UV-Vis, XPS, and ESR. Their performance under visible-light irradiation was found to be significantly influenced by the amount of Ag doping, the calcination temperature and the air contact area. The results demonstrated higher Ag doping greatly enhanced the degradation of HCHO. The photocatalytic degradation efficiency of HCHO over 2%Ag/Bi-TiO2 reached 87.5 %, which was significantly higher compared to Bi-TiO2 (74.0 %) and TiO2 (65.6 %), and the concentration of HCHO decreased from 1.069 to 0.134 mg/m3 within 48 h. The heterostructure of Ag2O/Ag and Bi-TiO2 facilitated effective electron transfer and suppressed the recombination of electron-hole pairs. The enhanced adsorption of visible-light and the improved photocatalytic performance were attributed to the synergistic effect of surface hydroxyl and adsorbed oxygen.

A versatile electrospun polylactic acid nanofiber membrane integrated with halloysite nanotubes for indoor air purification, disinfection, and photocatalytic degradation of pollutants

Electrospinning nanofiber membranes (ENMs) have been studied extensively as high-efficient air filters, but still subject to low filtration efficiency for submicron PMs and limited function. Meanwhile, filters based on ENMs originated from petroleum seriously increase the burden on the environment. Polylactic acid (PLA), a bio-based biodegradable polymer with non-biotoxicity, degradability, and environmental sustainability, is a highly promising material from air purification perspectives. However, it is still a challenge to improve the air filtration performance, disinfection, and formaldehyde degradation of PLA ENMs simultaneously. Here, we feasibly present a versatile PLA ENMs integrated with natural electret halloysite nanotubes (HNTs) and silver phosphate (Ag3PO4) via the electrospinning assisted with spraying technology and continuous winding device. The HNTs improves the free-standing properties of the PLA ENMs and endows it with electret effect, which can enhance the electrostatic interaction with submicron PMs and bacteria as well as extend the service life. Furthermore, Ag3PO4 was distributed onto HNTs and then incorporated into PLA nanofiber which enables HNTs@Ag3PO4/PLA ENMs to display a remarkable disinfection and good photodegradation ability towards gaseous formaldehyde. Additionally, the HNTs@Ag3PO4/PLA ENMs exhibits excellent photodegradation ability towards methylene blue and tetracycline under the visible light irradiation, effectively solving the problems such as difficult separation and recovery of powdery photocatalysts. Such PLA based composite membrane with enhanced electrostatic interaction and photocatalytic property could show the versatilities, e.g. improving the efficiencies and service life on filtering PMs, killing bacteria, degrading VOCs, etc., which provides a new idea and feasible method for purifying indoor air and water based on green polymer and electrospinning technology.

The performance investigation on a multifunctional wall with photo-thermal catalytic blinds for heating, shading and formaldehyde removal

A novel multifunctional wall with photo-thermal catalytic blinds (PTC-Blind/TW) for heating, shading and formaldehyde removal was proposed. The system can realize indoor air purification all year by using solar energy, space heating in winter and cooling in summer simultaneously. The hybrid wall system was built and thermal and formaldehyde degradation performance was tested experimentally. The coupled heat, mass and reaction dynamic model was established and experimentally verified. Based on the model, the optimal blind angle control strategy was studied when the system runs in different cities all year. Main results were: (1) Under the solar radiation of 300–900 W/m2, the thermal efficiency, formaldehyde single-through convention and CADR of system were in the range of 20–40%, 30–60% and 20–80 m3/h respectively. (2) For the thermal and purification performance of the system, the fitted degree R2 between the simulation results and the experimental results reaches 80–90%. (3) The optimal blind turning angle operation strategy in Nanjing, Beijing, Xining and Guangzhou was obtained. (4) When applied optimal operation strategy in four cities, the total generated clean air annually, reduced heating loads in winter seasons and reduced cooling loads in summer and transition seasons were in range of 0.8–1.7*104 m3/m2, 86.3–739.5 MJ/m2 and 261.2–388.5 MJ/m2 respectively.

Multi-contact prismatic spiky block titanium dioxide–graphene covalent composites for formaldehyde degradation

In this study, in situ solvothermal growth was carried out to fabricate multi-contact prismatic spiky block TiO2–graphene covalent composites (PTG) with unique morphologies. Prismatic conical TiO2 projections were uniformly formed on graphene sheets, yielding block PTG with Ti–C and Ti–O–C covalent bonds. The crystal structure and morphological properties of PTG were characterized, and its photocatalytic performance was evaluated. The covalent doping of graphene sheets resulted in the superior gaseous formaldehyde degradation activity of PTG compared to that of prickly spherical TiO2, with a degradation rate of 80.1% under visible light after 120 min. Electron paramagnetic resonance spectroscopy revealed that PTG displayed a sustained radical response and maintained high catalytic activity after five cycles of formaldehyde degradation. The reliable cycling stability and visible-light-induced photocatalytic activity of PTG suggest its potential for application in the field of hazardous gas degradation.

A novel Trombe wall with photo-thermal synergistically catalytic purification blinds: Material and experimental performance study

Trombe wall is a widely used solar heating structure, but still has problems of easy accumulation of indoor pollutants and overheating. The photo-thermal catalytic purification technology can use solar full spectrum for air purification and heating. Thus, a Trombe wall with photo-thermal synergistically catalytic blinds was proposed, which realized heating and formaldehyde purification in winter and shading in summer. Firstly, the photo-thermal composite catalysts with different photo/thermal catalyst ratios were prepared and the formaldehyde degradation under different catalytic conditions was conducted. Then an experimental test system was built to explore the thermal and formaldehyde degradation performance under three blind turning angles of 15°, 45° and 75°. The results were: (1) The formaldehyde degradation performance was the best when the ratio of photo-thermal catalyst was 10%. (2) The solar radiation reduced the activation energy of photo-thermal catalysts by 14.5%–31.3%, which revealed a photo-thermal synergistic catalytic effect. (3) Indoor steady experiments showed that the comprehensive performance of wall increased with the solar radiation intensity and blind angle. (4) The outdoor experiments showed the wall behaved best performance when the blind turning angle was 45°. The thermal efficiency and total generated clean air could reach 40.9% and 205.1 m3 at daytime, respectively.

A ventilated wall integrated with heating/catalytic blinds: Catalyst, system design and performance study

A Trombe wall with thermal catalytic blinds (TC-Blind/TW) for indoor heating/cooling, air purification and shading was proposed. In this paper, we has fully explored the advancement and feasibility of the system from thermal catalytic material preparation and performance testing, system construction and system steady state experiment testing, system heat-mass transfer model establishment and verification, and finally to the analysis of system operation strategy. The main conclusions are as follows: Firstly, thermal catalytic material MnOx-CeO2 behaved excellent heating and purification performance, the formaldehyde degradation followed L-H model. Secondly, the thermal efficiency and formaldehyde single-through conversion of system during the daytime were between 35%-55% and 32%–42%, respectively. Thirdly, the established heat-mass transfer model had the high accuracy, with the maximum RSMD of 0.8%. Finally, the blinds turning angle has a great influence on the system performance, then the optimal annual operation angles in four cities were suggested. Take Beijing as an example, the annual generated clean air was 11355.6 m3/m2, the reduced heating and cooling loads were 341.2 and 318.3 MJ/m2, respectively.

Biodegradation and process optimization of phenol and formaldehyde by Aspergillus nomius SGFA1

Phenols and formaldehyde are often simultaneously discharged into the environment with sewage, and due to their highly toxic to organisms, few have been reported to be degraded simultaneously. This study investigated the simultaneous biodegradation of phenol and formaldehyde using the highly efficient formaldehyde-degrading fungus Aspergillus nomius SGFA1, which was previously isolated and identified in our laboratory. The response surface methodology was used to optimize the biodegradation conditions of phenol and formaldehyde; the optimum temperature, initial pH, and glucose content were determined to be 28.1 °C, 5.0, and 0.89%, respectively, under which the maximum degradation rates of phenol and formaldehyde reached 89.7% and 85.3%, respectively. Mass balance and stoichiometric analysis revealed 0.26 g⋅g−1 and 0.05 g⋅g−1 conversions of phenol and formaldehyde carbon to biomass, respectively. The degradation pathway demonstrated that phenol hydroxylase (PHE) and formaldehyde dehydrogenase (FALDH) were the key enzymes for phenol and formaldehyde degradation, with enzyme activities reaching maxima of 0.008 and 1.09 U⋅mg−1 at 8 and 6 h, respectively. This study demonstrated the ability of A. nomius SGFA1 to effectively remove phenol and formaldehyde simultaneously, providing new information on the use of microorganisms to reduce environmental pollution.

From waste to wealth: a cellulose-based fibrous membrane from recycled cigarettes supported with dual perovskite for formaldehyde degradation at room temperature

Formaldehyde, as a hazardous indoor contaminant following house decoration, is essential to its efficient removal at room temperature. This paper reports an eco-friendly approach for extracting cellulose acetate (CA) from waste cigarette filters to construct a nanofibrous composite membrane for formaldehyde degradation at ambient temperature. A composite nanofibrous membrane was fabricated by salable electrospinning of cellulose acetate and La2CoMnO6/CeO2 (LC), followed by hydrolysis and potassium doping with KOH. The membrane demonstrates excellent catalytic activity (97.56% of conversion), super stability (95.35% of conversion after 50 h) and long service life (93.96% of conversion after 3 catalysis cycles), which is ascribed to the synergistic catalytic effect of double perovskite and rapid hygroscopic properties of cellulose. In addition, the obtained membrane has a higher moisture regain (7.82%) than that of the LC/CA nanofibrous membrane (2.21%), and higher than that of the commercial air filter membrane using polypropylene (PP) fiber (near zero), accelerating formaldehyde adsorption and fastening the water removal, thereby allowing for the long-term positive progress of formaldehyde catalytic oxidation reaction. This work provides encouraging guidance for further exploration into formaldehyde degradation, which is promising for application in air cleaning.

Electro-injection-enhanced catalytic formaldehyde degradation based on conductive MnOx cellulose aerogels at room temperature

Transition metal oxide MnOx shows great potential in catalytic formaldehyde (HCHO) pollution degradation at room temperature, but it is difficult to effectively overcome the catalyst deactivation caused by the accumulation of intermediates. Hereon, a 3D conductive aerogel catalyst with cellulose nanofibers (CNF) skeleton supported MnOx nanoflowers and carbon black (CB) was prepared by freeze-drying. Based on the aerogel catalyst (MnOx/CB/CNF), an electro-injection-enhanced catalytic oxidation (EICO) strategy was proposed for HCHO degradation by promoting the formation lattice oxygen and reactive oxygen species O* . In the dynamic test (∼15 ppm at the weight hourly space velocity (WHSV) of 600000 mL/gMnOx·h), the HCHO-to-CO2 conversion efficiency of MnOx/CB/CNF by electro-injection can be enhanced to 76.27%, which is 26.4% higher than that without electro-injection, and the corresponding dynamic efficiency did not show a decreasing trend within 72 h. This proposed EICO strategy may realize the efficient and long-term pollutant degradation at room temperature.

The experimental and theoretical analysis on a Trombe wall with photo-thermal composite catalytic purification blinds

Trombe wall is one of typical solar passive heating systems, while exists issues of single-function and indoor air pollution. The photo-thermal synergistically catalytic technology has huge advantage on applying solar energy for heating and air purification. This article proposed a Trombe wall with photo-thermal catalytic purification blinds, which realized air purification, space heating and shading. Firstly, the catalytic activity and mechanism of photo-thermal catalytic material MnOx-CeO2/TiO2 were investigated. Then the experimental and model study on the thermal and formaldehyde degradation performance of proposed wall under three blind angles were conducted. Finally, the parameter and energy-saving performance were investigated. The results show that: Firstly, the once-through conversion of MnOx-CeO2/TiO2 with optimal photocatalyst/thermal-catalyst ratio of 10% approached 80% when the catalytic temperature was above 40 °C. The solar radiation decreased the catalytic reaction activation energy and a photo-thermal synergetic catalytic effect was existed. Secondly, the wall had optimal performance when the blind angle was 45° among the three angles of 15°, 45° and 75° explored in the experiment. In a sunny winter day, the air thermal efficiency and total generated clean air approached 40.9% and 205.2 m3/day, respectively. Thirdly, the thermal and formaldehyde degradation performance increased with solar radiation, ambient temperature and air channel height, while the air channel thickness had an optimal value. Finally, the optimal annual blind operation angles in Hefei were suggested. The average annual volume of clean air generated was 46 m3/day, the total reduced heating and cooling loads were 225.8 MJ/m2 and 616.0 MJ/m2, respectively.

The impact of operational factors on degradation of formaldehyde as a human carcinogen using Ag3 PO4 /TiO2 photocatalyst.

Background: The International Agency for Research on Cancer (IARC) identified formaldehyde as a carcinogen in 2004, yet formaldehyde is widely used in health care settings and various industries. In recent years, photocatalytic oxidation has been developed as a potential technique for removing pollutants arising from organic chemical agents and consequently promoting the health indices. This study investigated the effect of operational factors in optimizing formaldehyde removal from the air using Ag3 PO4 /TiO2 photocatalyst. Methods: An experimental study was designed to investigate the effect of operational factors on the efficiency of formaldehyde degradation. The variables investigated in this study include pollutant retention time, initial pollutant concentration and relative humidity. Sol-gel method was used to synthesize the nano-composite photocatalyst. An ideal experimental design was carried out based on Box-Behnken design (BBD) with response surface methodology (RSM). The sample size in this study includes all the glasses coated with Ag3 PO4 /TiO2 photocatalyst. Results: The maximum formaldehyde degradation of 32% was obtained at the initial concentration of 2 ppm, 20% relative humidity, and 90 minutes of retention time. Based on the statistical results, the correlation coefficient of the present study for the impact of operational factors on formaldehyde degradation was 0.9635, which means that there is only 3.65% probability of error in the model. Conclusion: The operational factors examined in this study (retention time, relative humidity, and initial formaldehyde concentration) were significantly influential in the degradation efficiency of formaldehyde by the photocatalyst. Due to the high exposure of employees and clients of health and treatment centers to formaldehyde as a carcinogenic substance, the results of this study can be used in ventilation systems to remove environmental pollutants in health care centers and other occupational settings.

Photocatalytic degradation of formaldehyde by ruthenium vanadate quantum dots-V2O5 nanowires array

In this work, ruthenium vanadate quantum dots-V2O5 nanowire arrays are prepared by hydrothermal, ion-exchange and calcination methods, and used for photocatalytic degradation of formaldehyde. The photocatalytic properties of the samples obtained at different calcination temperatures are tested and compared in detail. It is found that the sample calcined at 400 ℃ has a significantly enhanced light absorption due to a large number of uniformly distributed ruthenium vanadate quantum dots and oxygen vacancies on the nanowires. The formaldehyde degradation rate is 98% under 45 min illumination. Compared with the first cycle, the photocatalytic performance of the sample tested 4 cycle maintains 96%. This work provides a fabrication method of ruthenium vanadate quantum dots for effectively improving the light absorption and promoting the application of photocatalyst in the degradation of formaldehyde.

Thermocatalytic Degradation of Gaseous Formaldehyde Using Transition Metal-Based Catalysts.

Formaldehyde (HCHO: FA) is one of the most abundant but hazardous gaseous pollutants. Transition metal oxide (TMO)-based thermocatalysts have gained much attention in its removal due to their excellent thermal stability and cost-effectiveness. Herein, a comprehensive review is offered to highlight the current progress in TMO-based thermocatalysts (e.g., manganese, cerium, cobalt, and their composites) in association with the strategies established for catalytic removal of FA. Efforts are hence made to describe the interactive role of key factors (e.g., exposed crystal facets, alkali metal/nitrogen modification, type of precursors, and alkali/acid treatment) governing the catalytic activity of TMO-based thermocatalysts against FA. Their performance has been evaluated further between two distinctive operation conditions (i.e., low versus high temperature) based on computational metrics such as reaction rate. Accordingly, the superiority of TMO-based composite catalysts over mono- and bi-metallic TMO catalysts is evident to reflect the abundant surface oxygen vacancies and enhanced FA adsorptivity of the former group. Finally, the present challenges and future prospects for TMO-based catalysts are discussed with respect to the catalytic oxidation of FA. This review is expected to offer valuable information to design and build high performance catalysts for the efficient degradation of volatile organic compounds.

Self-Luminous Wood Coatings with Carbon Dots/TiO2 Grafted Afterglow SrAl2O4: Eu, Dy Core-Shell Phosphors for Long-Lasting Formaldehyde Removal.

Long-term relief of indoor volatile pollution has become a competitive issue worldwide in both visible and dark environments. A novel self-luminous wood coating with carbon dots (CDs)/titanium dioxide (TiO2) nanomaterial coated SrAl2O4: Eu2+, Dy3+ (CDs/TiO2@SAO) composite was prepared for the long-term degradation of formaldehyde through a simple sol-gel method. The microstructure, chemical composition, ultraviolet-visible (UV-vis) spectra, and long-lasting fluorescence of the CDs/TiO2@SAO photocatalyst were analyzed to illustrate the mechanism for degrading formaldehyde. The obtained CDs with a particle size of ~2-7 nm have a good graphite structure and presented good absorption in visible light. In addition, owing to the synergistic effect of the CDs/TiO2 nanomaterial coating layer and the long-afterglow luminescence of the SAO phosphor, the CDs/TiO2@SAO composite can absorb a part of the visible light for photocatalytic degradation and store luminous energy efficiently at daytime so as to give out visible luminescence continuously for a few hours in the darkness. Furthermore, the functional wood coatings with CDs/TiO2@SAO composite presented continuous and efficient photocatalytic activity in the presence and absence of light exposure. The current research could provide a new strategy for designing an efficient photocatalyst for degrading formaldehyde pollution in the daytime with a visible light supply and in an indoor dark environment without an external light source.

High-efficient capture and degradation of formaldehyde based on the electric-field-enhanced catalytic effect

Enhancing the generation of active groups is of great significance for alleviating the catalyst deactivation of formaldehyde (HCHO) by accelerating the decomposition of intermediate products. Herein, an electric-field-enhanced catalytic effect was proposed for the efficient capture and degradation of HCHO base on carbon cloth loaded manganese oxide catalyst (MnOx-CC). Under the action of electric field, MnOx can generate more hydroxyl radicals (•OH) and superoxide radicals (•O2-), thus accelerating the degradation of HCHO and intermediates at room temperature. After the introduction electric field (∼1 ×104 V/m), •O2- and •OH radical on the surface of MnOx-CC catalyst can be increased by 8 times and 23 times, respectively. At weight hourly space velocity of 300,000 mL/(gcat h) for ∼15 ppm HCHO, MnOx-CC-Electric Field catalyst reached the removal efficiency of 99.4%, and the CO2 conversion efficiency of 81.2%, without decrease significantly within 80 h. Theoretical calculation shows that the electric field can increase the electron state density of Mn atom at the Fermi level and reduce the adsorption energy of HCHO, O2 and H2O, thus promoting the generation of active groups and degradation of intermediate products. The electric-field-enhancement catalytic effect provides a new approach for the degradation of Volatile Organic Compounds.