Degradation Of Formaldehyde Research Articles

Enhanced photo-assisted thermal catalytic oxidation of formaldehyde via abundant surface adsorbed oxygen in Co3O4 with the assistance of natural zeolite

Photo-assisted catalytic oxidation is a promising and sustainable method for the formaldehyde (HCHO) degradation. Catalyst loading and surface adsorbed oxygen species are common strategies to enhance the efficiency of photo-assisted catalytic oxidation. In this work, acid-treated zeolite-based natural zeolites (mordenite and stellerite) were used as supports, to obtain Co3O4-natural zeolite composites by impregnation and MOF-templated methods. Under the combined action of visible light irradiation and heat condition, the photo-assisted thermal catalytic performance of different composites was determined. Among these composites, the Co-AS (Co3O4-acid-treated stellerite) composite exhibited the best HCHO mineralization performance. The use of acid-treated stellerite as a catalyst carrier effectively reduced the crystallite size of Co3O4, improved its dispersibility, and increased the surface adsorbed oxygen species, contributing to enhanced catalytic efficiency. The in-situ DRIFTs results showed that the main intermediates of photo-assisted thermal catalysis degradation were dioxymethylene (DOM) and HCOO-. Additionly, the reusability performance of the composites was also investigated. Experimental results showed that the composite had good photo-assisted thermal catalytic performance and durability, making it a promising catalyst for indoor air purification.

Piezoelectric photocatalytic degradation of formaldehyde based on BFO@OCN heterojunctions

Piezoelectric photocatalysts represent a new class of environment-cleaning materials containing a self-electricity nanogenerator. Wind is one of the common energy sources in the natural environment. The piezoelectric field generated by the action of wind on piezoelectric materials can promote the adsorption of organic pollutants and also facilitate the transfer and separation of photogenerated carriers, thereby improving the efficiency of photocatalytic degradation of formaldehyde. This work developed a BFO@OCN heterojunction composite combing BiFeO3 nanocubes (BFO) and g-C3N4 nanosheets with oxygen vacancies (OCN). This piezoelectric photocatalyst exhibited high activity in degradation of formaldehyde in gas under light irradiation. Within 90 min, the formaldehyde concentration reduced from 1.50 ppm to 0.68 ppm, almost 2 times higher than the pure CN. This enhanced catalytic performance can be attributed to the synergistic interplay between the wind-induced piezoelectric field generated by BFO nanocubes in wind and the heterojunction with oxygen vacancies from g-C3N4 nanosheets. The piezoelectric field promoted the transfer of photoelectrons and holes in opposite directions, which could inhibit their recombination. Meanwhile, it also induced the generation of oxygen vacancies from g-C3N4 nanosheets. Our research findings provided a feasible strategy for developing high-efficiency piezoelectric photocatalysts, which could be decorated on the car outer-surface for self-cleaning and air purification under sunlight irradiation.

Fabrication of CoTiO3/MgIn2S4 S–scheme heterojunctions with efficient charge separation to enhance the photocatalytic activities of hydrogen generation and formaldehyde removal

The efficient separation of photoinduced charge carriers is a primary factor in the catalytic performance of photocatalysts. Constructing S-scheme heterojunctions is a prospective strategy to efficiently and spatially separate photoinduced charges while retaining strong oxidation and reduction capacities of the catalyst system. Herein, CoTiO3/MgIn2S4 (abbreviated x% CTO/MIS, where x% represents the mass ratio of CTO-to-MIS; x = 5, 10, 15, 20, and 25) heterojunctions were successfully synthesized using a hydrothermal method. These heterojunctions exhibited highly efficient and reusable visible-light photocatalytic properties for hydrogen (H2) generation and formaldehyde (HCHO) degradation. Notably, the 15 % CTO/MIS demonstrated an admirable H2 evolution activity of 631.77 μmol·g−1·h−1, with AQE = 2.25 % at λ = 420 nm, and an HCHO degradation rate of 67.18 %. The intermediate products generated during HCHO removal were identified applying in situ diffuse reflectance infrared Fourier transform spectroscopy. The exceptional catalytic performance of the synthesized materials was attributed to the boosted light absorption and utilization, rapidly separation, and transfer of photoproduced charge carriers, which resulted from the internal electric field of the S-scheme mechanism. Moreover, the S-scheme electron transfer pathway for the CTO/MIS catalyst system during the photocatalytic process was confirmed using electron spin resonance spectroscopy, free-radical capturing tests, density functional theory calculations, in situ X-ray photoelectron spectroscopy, and semiconductor energy band theory. The study offers an innovative perspective for establishing S-scheme heterojunctions with highly efficient and stable photocatalytic activity for H2 generation and HCHO removal.

Efficient visible-light-driven photocatalytic degradation of indoor formaldehyde using an indium-based MOF/graphene oxide composite

Formaldehyde (HCHO) severely degrades indoor air quality, and conventional remediation methods are often inadequate for addressing low concentrations of HCHO indoors. In this study, we synthesized a MIL-68(In)-NH2/graphene oxide (GO) composite using a solvothermal method, aimed specifically at enhancing the photocatalytic degradation of HCHO under visible light. Our results show that the integration of GO enhances visible light absorption and facilitates efficient electron transport, significantly improving photocatalytic performance. The MIL-68(In)-NH2/GO composite achieves a 77 % degradation rate of HCHO, significantly outperforming MIL-68(In)-NH2 (51 %) and GO (22 %) alone. This enhanced activity is attributed to the effective separation of electron-hole pairs and synergistic interactions within the composite. We proposed an enhanced photocatalytic mechanism for the MIL-68(In)-NH2/GO system, identifying h+ and •O2– as the principal active species. Moreover, the MIL-68(In)-NH2/GO composite shows excellent reusability and stability, making it a promising candidate for eco-friendly and efficient indoor air purification using metal–organic frameworks.

Multifunctional air filter with enhanced filtration, formaldehyde degradation, and antibacterial properties using PET, PDA, and RGO-TiO2

Currently, most air filters, such as polyester (PET) fiber non-woven fabric, only have a single function of particulate filtration. However, the removal of substances harmful to human health, such as volatile organic compounds (VOCs) and bacteria, is becoming increasingly important in indoor air purification. Herein, based on the biomimetic surface functionalization properties of polydopamine (PDA) and the photocatalytic degradation of organic matter and the antibacterial effect of RGO (reduced graphene oxide)-TiO2, a multifunctional NWP2/PET-PDA-RGO-TiO2(P/PPRT) filter with a sandwich structure was prepared for formaldehyde degradation, aerosol filtration, and bactericidal operation. The P/PP2R0.05T20 maintains optimal performance of photocatalytic reaction kinetics and reaches a formaldehyde degradation rate of higher than 79 % within 300 min in the 7th cycle of usage. Compared with the base subtracts, P/PP2R0.05T20 has the highest filtration efficiency of 88.57–99.18 % for 0.3–10 µm particles, respectively, and has a filtration efficiency of higher than 74 % for 0.3 µm particles in the 7th cycles of usage. The quality factor of P/PP2R0.05T20 is improved significantly due to the sandwich structure. The effect of loaded particulate on the catalyst for photocatalytic degradation of formaldehyde was also studied. It was found that the photocatalytic formaldehyde degradation rate of P/PP2R0.05T20 is about 81.8 % within 300 min under different A2 particulate load content. In addition, P/PP2R0.05T20 has a bioaerosol removal rate of higher than 98 % against E. coli. This study provides a practical approach to preparing a multifunctional air filter with the performance of aerosol filtration, photocatalytic degradation of formaldehyde, and bactericidal function using PET non-woven fabric.

Generation of oxygen vacancies in CuO/TiO2 heterojunction induced by diatomite for highly efficient UV–Vis-IR driven photothermal catalytic oxidation of HCHO

Photothermal catalytic oxidation is a promising and sustainable method for the degradation of indoor formaldehyde (HCHO). However, the excessively high surface temperature of existing photothermal catalysts during catalysis hinders the effective adsorption and degradation of formaldehyde under static conditions. Catalyst loading and oxygen vacancies (OVs) modulation are commonly employed strategies to reduce the photothermal catalytic temperature and enhance the efficiency of photothermal catalytic oxidation. In this work, a p-n type CuO/TiO2 heterojunction is successfully loaded onto diatomite using a wet precipitation method. Under the irradiation of a 300W xenon lamp, the prepared composite material achieved a 100% removal rate of HCHO within 2 h, with a 98% conversion rate to CO2, surpassing the performance of both individual photocatalysts and thermocatalysts. Additionally, by adjusting conditions such as light irradiation and temperature, we have demonstrated that this material exhibits synergistic photothermal catalytic properties. Based on HRTEM, XPS, Raman, and EPR analyses, the introduction of diatomite as a catalyst support was shown to effectively increase the number of OVs. Experimental results, along with O2-TPD, photoelectrochemical characterization, and radical detection, demonstrate that the presence of OVs enhances the oxidative efficiency of both photocatalysis and thermocatalysis, as well as the UV–Vis-IR photothermal catalytic performance. The ternary composite material generates weak hydroxyl (•OH) and superoxide (•O2−) radical under high-temperature with dark conditions, indicating its catalytic oxidation activity under this condition. The increase in temperature and the expansion of the spectral range both enhance the generation of these radicals. In summary, this work demonstrates that the use of diatomite as a support increases the material's specific surface area and OVs content, thereby enhancing adsorption and photothermal catalysis. It elucidates the enhanced catalytic degradation mechanism of this mineral-based photothermal catalyst.

Novel resource utilization of fly ash and blast furnace slag for formaldehyde-degrading alkali-activated cementitious composite

Herein, alkali-activated cementitious materials (AACM) were fabricated using fly ash and blast furnace slag as raw materials, while foamed alkali-activated cementitious materials (FAACM) were prepared by a physical foaming method. They were regarded as suitable supporting carriers to load nano-TiO2 by a three-layered method and blending-foaming method to synthesize TiO2-AACM and TiO2-FAACM, respectively. The relationship between the microstructure of the alkali-activated cementitious composites with the photocatalytic activity and stability of formaldehyde degradation was revealed. The nano-TiO2 blended with AACM and FAACM exhibited good mechanical properties. Moreover, a systematic mechanism study revealed that the incorporation of nano-TiO2 did not change the hydration products of composites. There were similar forbidden bandwidths in TiO2-AACM and TiO2-FAACM compared with nano-TiO2, as nano-TiO2 was not involved in geopolymerization. The degradation efficiency of formaldehyde by TiO2-AACM and TiO2-FAACM attained 52.21 % and 55.02 %, respectively, at an initial formaldehyde concentration of 20 ppm after illumination (300 W Xe lamp) of 2 h. It was found that the excellent porous structure of FAACM promoted the adsorption efficiency of formaldehyde in the composites, which contributed to the higher photocatalytic degradation efficiency of formaldehyde. Compared with Portland cement, the CO2 emission of alkali-activated cementitious materials made from fly ash and blast furnace slag was decreased by 61.28 %. This research promotes the comprehensive utilization of solid wastes for developing the functionalized application of green materials.

Clarifying the Direct Generation of •OH Radicals in Photocatalytic O2 Reduction: Theoretical Prediction Combined with Experimental Validation.

This work systematically studied thermocatalytic and photocatalytic pathways of formaldehyde degradation and H-assisted O2 reduction over a Pt13/anatase-TiO2(101) composite via DFT calculations together with constrained molecular dynamics (MD) simulations. We show that photocatalytic O2 reduction on Pt/TiO2 can directly generate •OH radicals (*O2 → *OOH → •OH) via two hydrogenation steps with small barriers, and the product selectivity (*H2O2 or •OH) is decided by the relative position between catalyst Fermi level and •OH/*H2O2 redox potential (theoretical determination of 0.07 V referencing to the SHE). Such a novel reaction channel was furthermore validated at the liquid-solid interface via constrained MD simulations and experimental electron paramagnetic resonance detections, and a wide range of H resources, e.g., *HCHO, *HCO, *H (H+ + e-), can always drive the direct •OH generation. The additional portion of e--triggered •OH radicals are prone to diffuse into solution or the TiO2 surface and furthermore cooperate with the conventional h+-driven photooxidations.

Oxygen vacancy–rich K-Mn3O4@CeO2 catalyst for efficient oxidation degradation of formaldehyde at near room temperature

Synthesis of catalysts with high catalytic degradation activity for formaldehyde (HCHO) at room temperature is highly desirable for indoor air quality control. Herein, a novel K-Mn3O4@CeO2 catalyst with excellent catalytic oxidation activity toward HCHO at near room temperature was reported. In particular, the K addition in K-Mn3O4@CeO2 considerably enhanced the oxidation activity, and importantly, 99.3 % conversion of 10 mL of a 40 mg/L HCHO solution at 30 °C for 14 h was achieved, with simultaneous strong cycling stability. Moreover, the addition of K species considerably influenced the chemical valence state of Mn from +4 (ε-MnO2) to +8/3 (Mn3O4) on the surface of CeO2, which obviously changed the tunnel structure and the number of oxygen vacancies. One part of K species is uniformly dispersed on K-Mn3O4@CeO2, and the other part exists in the tunnel structure of Mn3O4@CeO2, which is mainly used to balance the negative charge of the tunnel and prevent collapse of the structure, providing enough active sites for the catalytic oxidation of HCHO. We observed a phase transition from tunneled KMnO2 to Mn3O4 to tunneled MnO2 with the decreasing K+ content, in which K-Mn3O4@CeO2 exhibited higher HCHO oxidation activity. In addition, K-Mn3O4@CeO2 exhibited lower oxygen vacancy formation and HCHO adsorption energies in aqueous solution based on density functional theory calculations. This is because the K species provide more active oxygen species and richer oxygen vacancies on the surface of K-Mn3O4@CeO2, promote the mobility of lattice oxygen and the room-temperature reduction properties of oxygen species, and enhance the ability of the catalyst to replenish the consumed oxygen species. Finally, a possible HCHO catalytic oxidation pathway on the surface of K-Mn3O4@CeO2 catalyst is proposed.

Preparation of Perovskite-Type LaMnO3 and Its Catalytic Degradation of Formaldehyde in Wastewater.

Formaldehyde (HCHO) is identified as the most toxic chemical among 45 organic compounds found in industrial wastewater, posing significant harm to both the environment and human health. In this study, a novel approach utilizing the Lanthanum-manganese complex oxide (LaMnO3)/peroxymonosulfate (PMS) system was proposed for the effective removal of HCHO from wastewater. Perovskite-Type LaMnO3 was prepared by sol-gel method. The chemical compositions and morphology of LaMnO3 samples were analyzed through thermogravimetric analysis (TG), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The effects of LaMnO3 dosage, PMS concentration, HCHO concentration, and initial pH on the HCHO removal rate were investigated. When the concentration of HCHO is less than 1.086 mg/mL (5 mL), the dosage of LaMnO3 is 0.06 g, and n(PMS)/n(HCHO) = 2.5, the removal rate of HCHO is more than 96% in the range of pH = 5-13 at 25 °C for 10 min. Compared with single-component MnO2, the perovskite structure of LaMnO3 is beneficial to the catalytic degradation of HCHO by PMS. It is an efficient Fenton-like oxidation process for treating wastewater containing HCHO. The LaMnO3 promoted the formation of SO4•- and HO•, which sequentially oxidized HCHO to HCOOH and CO2.

In-situ immobilization of ZIF-67/ZIF-8 on wood biomass for degradation of methylene blue and formaldehyde

Metal-organic frameworks (MOFs) have been extensively studied for the removal of pollutants in wastewater and air. However, the existence of MOF materials in powder form with easy agglomeration and difficult separation has greatly confined their application potential. To address this challenge, ZIF-67/ZIF-8 composites were in-situ grown on wood biomass, with its porous structure providing channels for the growth of MOFs and active sites for MOFs catalysis. The structure, i.e., morphology, crystallinity and chemical components, and optical properties were characterized. The degradation efficiency of methylene blue (MB) by the ZIF-67/ZIF-8@wood composites photocatalyst was more than 85.7 % under visible light irradiation within 90 mins, reflecting the good photocatalytic activity of the composites. The ZIF-67/ZIF-8@wood composites completely adsorbed and decomposed HCHO (22.3 ppm) within 30 mins. The high catalytic performance of the ZIF-67/ZIF-8@wood composites can be attributed to the high surface area of wood that results in a high absorption of contaminants. This simple, low-cost, and green preparation method has promoted the sustainable utilization of biomass resources with great significance for practical environmental remediation.

Gas phase formaldehyde degradation: Continuous versus duty cycle driven plasma reactor

This study investigated the degradation of formaldehyde (HCHO) using continuous plasma reactor (CPR) and duty cycle driven plasma reactor (DCPR) to obtain insights into reactor selection, optimization strategies, and underlying kinetics. The electrical characteristics of the reactors were analyzed via current-voltage analysis while optical properties were investigated using optical emission spectroscopy (OES). Furthermore, the reactive species concentrations were determined using gas Fourier-transform infrared (FTIR) measurements. The optimization of the degradation focused on varying the applied voltages, resulting in intensified plasma and changes in the surface temperature, electron temperature rotational temperature, and vibrational temperature. CPR demonstrated outstanding efficiency, with an energy yield of 3.60 g kW−1 h−1 and an impressive 89 % removal effectiveness at 5.8 kV. The best removal efficiency of 92 % was observed at 6.2 kV. The degradation kinetics were primarily driven by energetic electrons, along with primary reactive species such as OH ⋅ and O ⋅ with a reaction rate of 6.8 × 10−3 L J−1. This study contributes to advancing the understanding of HCHO degradation kinetics and provides practical insights into enhancing plasma-based environmental cleanup technologies without using any catalyst.

In situ synthesis of mesoporous TiO2 doped with bismuth single atoms for tunable photocatalytic degradation of formaldehyde

Modification of a photocatalyst with single-atom metals to maximize atomic utilization and suppress charge carrier recombination is an effective strategy to dramatically improve the photocatalytic performance. Here we report the first successful development of the mesoporous TiO2 doped with Bi single-atom catalyst. The resulting single-atom photocatalyst possesses a narrower band gap structure, enhanced conductivity and outstanding photocatalytic activity driven by full spectrum light, which is 20 times higher than that of the commercial TiO2. As evidenced by photo-electrochemical characterizations and density functional theory (DFT) calculations, the Bi single atoms are confirmed to exhibit strong capacity to trap photo-generated electrons and probably act as the active sites in photocatalytic formaldehyde (CH2O) degradation. Additionally, reactive oxygen species (O2−, OH, and 1O2) were identified as key ingredients in promoting CH2O decomposition to CO2 and H2O. This innovative approach provides a promising method for fabricating mesoporous single-atom catalysts with tunable catalytic property.

Smart manufacturing of ZIF-8 photonic crystals: Catalytic formaldehyde degradation and colorful eco-friendly coatings

Formaldehyde and other harmful gases cause environmental pollution and threaten human health. Environment-friendly coatings is an effective strategy to address these environmental and health concerns. In this study, a large-scale amorphous photonic crystals (APC) based on modified ZIF-8 (Hxh-ZIF-8) with photocatalytic degradation of formaldehyde and tunable structural color were designed for eco-friendly coatings by programmable smart manufacturing. As APC unit, Hxh-ZIF-8 nanoparticles with controllable diameters were synthesized utilizing solvothermal method and the −N = C = O group was introduced with thermal oxidation. The results of photocatalytic degradation revealed that H5h-ZIF-8, through thermal oxidation, exhibited a formaldehyde degradation rate 9.8 times than that of ZIF-8. The main reactive components in photocatalysis were holes (h+) and superoxide radicals (·O2–), showcasing both stability and reproducibility. The color and brightness of the APC were adjusted by tuning the Hxh-ZIF-8 diameter. The angle-independent APC ranging from red to purple were fabricated with 177, 165 and 235 nm Hxh-ZIF-8 nanoparticles in various proportions with programmable smart manufacturing. In this study, a large-scale ZIF-8-based APC was designed with programmable smart manufacturing for environment-friendly coating, which combined environmental protection technology with structural color, and paved a new strategy for the development of multifunctional materials in air quality management.

Nanoarchitectonics of bamboo-based heterojunction photocatalyst for effective removal of organic pollutants

A high-performance photocatalyst with both efficient and reusable performance is essentially demanded for the purification of organic wastewater and the removal of indoor formaldehyde. However, recovery of photocatalyst particles from the reaction system remains a challenge. Herein, based on the abundant pore structure of natural bamboo and the outstanding photocatalytic activity of ZnO/WO3, we fabricated an efficient bamboo-based photocatalyst (ZnO/WO3@bamboo) for the efficient photocatalytic degradation of formaldehyde and organic dyes. The pretreatment of bamboo substrates with NaOH solution resulted in the formation of nucleation sites for ZnO/WO3 growth within bamboo cellulose channels. Subsequently, the as-prepared ZnO and WO3 were mixed in different mass ratios, and loaded on the pretreated bamboo substrates using the hydrothermal method. The results showed that the ZnO/WO3@bamboo had the effective function of photocatalytic degradation of formaldehyde gas and organic dyes. Moreover, the as-prepared ZnO/WO3@bamboo photocatalyst demonstrated superior recycling ability toward organic pollutants, which was described by photocatalytic degradation efficiency of formaldehyde gas more than 89% after 10 cycles, and organic dyes over 93% after 20 cycles. The coupling of ZnO and WO3 leads to electron delocalization, which caused the electron holes generated in the valence band (VB) of ZnO to delocalize to the VB of WO3, and reduced the recombination of electron-hole. Therefore, the photocatalytic degradation performance of the ZnO/WO3@bamboo was enhanced. The proposed ZnO/WO3@bamboo photocatalyst holds great promise in the field of air pollution and wastewater remediation.

Selective Heterogeneous Fenton Degradation of Formaldehyde Using the Fe-ZSM-5 Catalyst.

As a toxic Volatile Organic Pollutant (TVOC), formaldehyde has a toxic effect on microorganisms, consequently inhibiting the biochemical process of formaldehyde wastewater treatment. Therefore, the selective degradation of formaldehyde is of great significance in achieving high-efficiency and low-cost formaldehyde wastewater treatment. This study constructed a heterogeneous Fe-ZSM-5/H2O2 Fenton system f or the selective degradation of target compounds. By immobilizing Fe3+ onto the surface of a ZSM-5 molecular sieve, Fe-ZSM-5 was prepared successfully. XRD, BET and FT-IR spectral studies showed that Fe-ZSM-5 was mainly composed of micropores. The influences of different variables on formaldehyde-selective heterogeneous Fenton degradation performance were studied. The 93.7% formaldehyde degradation and 98.2% selectivity of formaldehyde compared with glucose were demonstrated in the optimized Fenton system after 360 min. Notably, the resultant selective Fenton oxidation system had a wide range of pH suitability, from 3.0 to 10.0. Also, the Fe-ZSM-5 was used in five consecutive cycles without a significant drop in formaldehyde degradation efficiency. The use of reactive oxygen species scavengers indicated that the hydroxyl radical was the primary active species responsible for degrading formaldehyde. Furthermore, great degradation performance was acquired with high concentrations of formaldehyde for this system, and the degradation efficiency was more than 95.0%.

Deactivation of layered MnO2 catalyst during room temperature formaldehyde degradation and its thermal regeneration mechanism

Layered δ-MnO2 prepared by a one-step redox method was shown to be deactivated during oxidation of formaldehyde at room temperature. Recovery of the formaldehyde degradation activity was investigated after thermal regeneration at different temperatures. XRD, SEM, TEM, H2-TPR, XPS, TGA and DRIFTS characterization were used to analyze the physical properties of fresh, deactivated and thermally regenerated catalysts. The results showed that deactivation of catalyst was caused by less oxygen vacancies due to increased Mn4+ content during formaldehyde degradation and formation of formate blocking active sites. Thermal regeneration helped to decompose formate at the catalyst surface, restoring some of the active sites. Interplanar spacing of MnO2 became wider and the number of Mn3+ on exposed crystal faces increased. More oxygen vacancies were formed. The activity of deactivated catalyst was restored. Formaldehyde degradation rate of catalyst regenerated at 200 °C remained above 80 % after 6 h, demonstrating the possibility of waste layered catalyst recycling.

Promoted oxygen adsorption on porous CeO2 cubes with abundant oxygen vacancies for efficient gaseous formaldehyde removal

Photocatalytic degradation stands as a promising method for eliminating gas-phase pollutants, with the efficiency largely hinging on the capture of photogenerated electrons by oxygen. In this work, we synthesized a porous CeO2 single crystal cube with abundant oxygen vacancies as photocatalyst, employing urea as a pore-forming agent and for gas-phase formaldehyde degradation. Compared with the CeO2 cubes without pores, the porous ones were superior in specific surface area, akin to conventional CeO2 nanoparticles. The photocatalytic degradation for gas-phase formaldehyde on porous CeO2 cubes was significantly accelerated, of which degradation rate is 3.3 times and 2.1 times that of CeO2 cubes without pores and CeO2 nanoparticles, respectively. Photoelectric tests and DFT calculations revealed that this enhancement stemmed from facilitated oxygen adsorption due to pronounced oxygen vacancies. Consequently, the capture of photoelectrons by oxygen was promoted and its recombination with holes was suppressed, along with an accelerated generation of curial free radicals such as ·OH. This work reveals the pivotal role of surface oxygen vacancies in promoting adsorbed oxygen, proposing a viable strategy to enhance the photocatalytic degradation efficiency for gas-phase pollutants.

Properties of multi-solid waste cementitious materials for highly efficient indoor formaldehyde degradation via response surface method

The environment-friendly cementitious materials with efficient indoor formaldehyde degradation properties (PRCS) were prepared by using slag to supplement the percentage of silica and aluminium in the phosphogypsum (PG)-red mud (RM) system, cement as an activator, and activation through the sulphate component in PG. PG-MnO2, a component of PRCS, was obtained by redox of potassium permanganate with PG as the carrier. The mechanism of formaldehyde degradation on PG-MnO2 was analyzed by catalytic model fitting, the multi-objective optimization of PRCS was achieved using response surface methodology (RSM), and the hydration products and microstructure of PRCS were characterized. The results show that the maximum compressive strength of PRCS can reach 26.02 MPa (7 days) and 35.13 MPa (28 days), respectively. The response surface model can be effectively used to simulate the compressive strength of PRCS since the experimental results of the best fitting ratio are close to the predicted results. PRCS achieves an initial 84 % degradation of formaldehyde through adsorption and surface active sites, and maintains 63 % efficiency after five degradation cycles. Also, there is no risk of heavy metal ion leaching.

Boosted photocatalytic performance of hydrogen evolution and formaldehyde degradation with a S-scheme PMo12/MgIn2S4 heterojunction

Fabrication of a S-scheme heterojunction with staggered energy band structures can accelerate the charge separation and retain high redox potentials. Herein, a series of x wt% H3PMo12O40/MgIn2S4 (abbr. x% PMo12/MIS; x = 7.5, 10.0, 12.5, 15.0 and 17.5) S-scheme heterojunctions were successfully constructed by a hydrothermal technology and exhibited efficient and durable visible-light-driven photocatalytic properties of H2-evolution and formaldehyde (HCHO) degradation. Particularly, the 12.5 % PMo12/MIS sample represented the optimal H2 evolution rate of 232.53 μmol·g−1·h−1 with the apparent quantum efficiency (AQE) value of 1.52 % (λ = 420 nm), and HCHO removal rate of 64.20 % in 60 min. Moreover, the intermediate products formed during the removal process of HCHO were revealed through in situ DRIFTS method. The superior photocatalytic activities mainly stemmed from the enhanced absorption of visible light, and effective separation of photoinduced charge carriers. Furthermore, the S-scheme photocatalytic mechanism for PMo12/MIS system was confirmed via in situ irradiated X-ray photoelectron spectroscopy, radical capturing tests and electron spin resonance data, and semiconductor energy band theory. The current study affords a valuable perspective for fabricating highly efficient S-scheme heterojunction photocatalysts for hydrogen evolution and HCHO elimination.