HCHO Conversion Research Articles

Cation induced electrostatic adsorption driven self-assembly sandwich-like α-MnO2/MXene for efficient self-heating photothermal synergistic catalytic decomposition of carcinogenic gaseous formaldehyde

Realizing self-assembly between different nanoparticles is an important strategy for constructing novel nanostructures or excellent functional composites. Formaldehyde is the primary gaseous pollutant in indoor air, and achieving its ambient temperature decomposition is of great significance for improving indoor air quality. This research reports an electrostatic adsorption driven self-assembly strategy, constructing a sandwich structure α-MnO2/MXene for self-heating photothermal synergistic catalytic decomposition of formaldehyde. The self-assembly process and electrostatic adsorption driven mechanism were detailed. A comparative study was conducted on the performance and mechanisms of the self-assembled sandwich structure and mechanically mixed α-MnO2/MXene in the self-heating photothermal catalytic decomposition of formaldehyde. The sandwich structure α-MnO2/MXene with built-in electric field and Schottky barrier exhibited excellent self-heating photothermal catalytic activity for formaldehyde decomposition, realizing the 100% mineralization of formaldehyde under simulated solar-light irradiation at room temperature; even with the irradiation of visible light, the sandwich structure α-MnO2/MXene can still maintain 82.6% HCHO conversion. Furthermore, we elucidated the self-heating photothermal catalytic mechanism, shedding light on the distinct roles and contributions of photocatalysis and thermal catalysis. It was found that the photothermal catalytic mechanism of the sandwich structure α-MnO2/MXene-S composite involved a thermally assisted photocatalytic process. The advantages of the self-assembled sandwich structure and its mechanism for enhancing photothermal performance were fully revealed. This study reports an effective strategy for electrostatic adsorption self-assembly, offering a fresh perspective on developing non-noble metal catalysts for ambient-temperature formaldehyde decomposition

Mesoporous Ag-K-Al2O3 catalysts prepared via a one-pot evaporation induced self-assembly approach and their application in catalytic oxidation of formaldehyde

Mesoporous Ag-Al2O3-m and Ag-K-Al2O3-m catalysts were fabricated by a one-pot technique based on an evaporation-induced self-assembly method. Among them, Ag-3 K-Al2O3-m exhibited the highest activity, achieving 100 % HCHO conversion at 40 °C. The catalyst’s performance was notably impacted by RH conditions, which showed improved activity at 30 % RH, due to the formation of active –OH groups. As the K loading increased, the aggregation of Ag particles gradually occurred. According to DFT computation, the presence of K promoted the adsorption and activation of HCHO, O2 and H2O on the catalyst surface. The superior low-temperature reducibility, adequate surface active oxygen and surface –OH groups were identified as key roles to the enhanced catalytic performance of Ag-K-Al2O3-m. Both Ag-Al2O3-m and Ag-K-Al2O3-m operated through the same oxidation mechanism for HCHO oxidation.

Sepiolite-Supported Manganese Oxide as an Efficient Catalyst for Formaldehyde Oxidation: Performance and Mechanism.

The current study involved the preparation of a number of MnOx/Sep catalysts using the impregnation (MnOx/Sep-I), hydrothermal (MnOx/Sep-H), and precipitation (MnOx/Sep-P) methods. The MnOx/Sep catalysts that were produced were examined for their ability to catalytically oxidize formaldehyde (HCHO). Through the use of several technologies, including N2 adsorption-desorption, XRD, FTIR, TEM, H2-TPR, O2-TPD, CO2-TPD, and XPS, the function of MnOx in HCHO elimination was examined. The MnOx/Sep-H combination was shown to have superior catalytic activities, outstanding cycle stability, and long-term activity. It was also able to perform complete HCHO conversion at 85 °C with a high GHSV of 6000 mL/(g·h) and 50% humidity. Large specific surface area and pore size, a widely dispersed active component, a high percentage of Mn3+ species, and lattice oxygen concentration all suggested a potential reaction route for HCHO oxidation. This research produced a low-cost, highly effective catalyst for HCHO purification in indoor or industrial air environments.

Multifunctional composite materials of rGO with RAFT initiated polymers with terminal amine or protonated amine functionalities for chemical eliminations HCHO and acidic pollutants at ambient conditions

In this paper, the contribution of self-assembled composite material of bifunctional polymer prepared by RAFT polymerization and rGO to the removal of low concentration HCHO and acids from air were systematically studied. Experimental results demonstrate that the condensation reaction between HCHO and the protonated amino group at the terminal of the rGO-py-pAMHS-NH3+-ph chain effectively can eliminate HCHO chemically, resulting in the release of H2O as the sole by-product following oxime bonds formation. rGO alone is incapable of chemically removing gaseous HCHO, but when combined with the py-pAMHS-NH3+-ph, efficient HCHO conversion can be achieved, well elucidating the remarkable HCHO removal capability via rGO-py-pAMHS-NH3+-ph. The HCHO chemical removal performance of composite is evaluated by a self-made device at the 1000 mL/min N2 velocity under 25 °C and 50 % RH and it is found that 206.41 mg of HCHO can be removed in approximately 4 h by using 1.0 g of rGO-py-pAMHS-NH3+-ph. In addition, cycling experiments demonstrate the rGO-py-pAMHS-NH3+-ph possesses good durability. We also find that the rGO-py-pAMHS-NH2-ph has the ability to remove acids when the terminal protonated amino groups have been converted into amine functionalities. This green and zero-carbon emission methodology for chemical removal of HCHO degradation and acid pollutants could provide valuable reference for developing other efficient strategies to remove other pollutants such as VOCs etc.

Construction of Pd@K-Silicalite-1 via in situ encapsulation and alkali metal modification for catalytic elimination of formaldehyde at room temperature

The Silicalite-1-encapsulated Pd catalyst with alkali metal K modification (Pd@K-Silicalite-1) was prepared via the hydrothermal method with ethylenediamine as ligand and KOH as precursor of K promoter. The introduction of K partially replaced H of silanol in Silicalite-1 and induced the formation of Si-O-K-Pd species, which were beneficial for the improvement of Pd dispersion. The Pd nanoparticles with a size of ca. 1.9 nm were uniformly encapsulated in the matrix of Silicalite-1 zeolite. The catalytic activity of Pd@K-Silicalite-1 was much better than those of Pd/Silicalite-1 and Pd@Silicalite-1 for HCHO oxidation, HCHO conversion could reach 100 % over Pd@K-Silicalite-1 (Pd content = 0.15 wt%) at room temperature under space velocity (SV) of 120,000 mL/(g × h) and relative humidity (RH) of 35 %. Based on the results of various characterization techniques, one can conclude that the improvement in catalytic activity of Pd@K-Silicalite-1 was attributable to high dispersion and small size of Pd NPs and enhanced HCHO adsorption capacities. In addition, we investigated the reaction mechanism of HCHO oxidation over the Pd@K-Silicalite-1 catalyst by in situ DRIFTS spectra. This work provides some guidance on developing high-performance catalysts for HCHO elimination via in situ encapsulation and alkali metal modification.

Cobalt enhanced (H/C-CdS)/CeO2 activity for visible light catalytic oxidation of formaldehyde at room temperature

The visible light catalytic oxidation of formaldehyde (HCHO) at room temperature is of great interest for improving the indoor air quality. Here, a cobalt (Co)-doped CdS-based catalyst ((H/C-CdS)/CeO2) with high visible light catalytic activity was successfully synthesized for HCHO removal at room temperature. Co addition enhanced the catalytic activity of (H/C-CdS)/CeO2, and the HCHO conversion rate reached 99.5 % for a 1 mg/L aqueous HCHO solution on the Co–(H/C-CdS)/CeO2 catalyst after 1 h at room temperature under visible light, which was greater than that of (H/C-CdS)/CeO2 (92.0 %). The (H/C-CdS)/CeO2 and Co–(H/C-CdS)/CeO2 catalysts were systemically characterized, and the results showed that the interfacial phase junction between the hexagonal (H) and cubic (C) phases of the CdS nanoparticles (NPs) and the synergistic effect of the type II heterojunction between the CdS NPs and CeO2 nanosheets (NSs) promoted the separation of e-/h+. Moreover, the addition of Co species strongly promoted the separation of photogenerated carriers. The excellent photocatalytic activity was attributed to the good dispersion of CdS NPs, which broadened the light absorption range, exposed more active sites, and provided close contact, decreasing the migration distance of photogenerated electron-hole pairs. After that, the visible light catalytic oxidation mechanism of HCHO on both (H/C-CdS)/CeO2 and Co–(H/C-CdS)/CeO2 followed the reaction pathway of HCHO to (CO2 + H2O).

Converting formaldehyde in methanol with MoO2 under irradiation: A pollution-free strategy for cleaning air

Direct photocatalytic reduction of toxic formaldehyde (HCHO) in value-added chemicals and fuels is promising because that not only abates the environmental pollution, but also solves the energy shortage. Herein, self-supported MoO2 and MoO3 nanoparticles growing on Mo meshes were comparatively applied to the photocatalytic conversion of HCHO. Under UV–visble lights, MoO2 reduces HCHO in methanol (CH3OH) while MoO3 oxidizes HCHO in carbon oxide and water. Their contrary photocatalytic capacities were revealed. Compared with MoO3, the lower work function of MoO2 enables an electron-rich interface, realizing a complete reduction of 30 ppm HCHO to CH3OH in 30 min. Theoretical calculations clarify that a large number of delocalized electrons on MoO2 attracts HCHO molecule and activates its CO bond, facilitating subsequent hydrogenation and reduction of HCHO to CH3OH. As for MoO3, the wider bandgap and higher potential of valence band govern the photocatalytic oxidation of HCHO.

Study on the mechanism of acid treatment La0.8Sr0.2Mn0.8Cu0.2O3 to improve the catalytic activity of formaldehyde at low temperature.

To address the issue of surface enrichment of A-site ions in perovskite and the resulting suppression of catalytic activity, the La0.8Sr0.2Mn0.8Cu0.2O3 was modified by treatment with dilute nitric acid (2mol/L) and dilute acetic acid (2mol/L). The results show that the effect of dilute nitric acid treatment on the morphology and catalytic activity of the catalyst is more significant. The specific surface area of the catalyst after dilute nitric acid treatment (268.78 m2/g) is seven times higher than before treatment (37.55 m2/g). The low-temperature catalytic oxidation activity of HCHO of the catalyst after dilute nitric acid treatment is significantly improved, achieving a 50% HCHO oxidation efficiency at 80 °C, while the original sample requires 127 °C to achieve a 50% HCHO conversion. The excellent catalytic activity of the catalyst after dilute nitric acid treatment is related to its large specific surface area, high surface-active site density, and abundant Mn4+ ions. Stability and water resistance experiments show that the catalyst after dilute nitric acid treatment has excellent reaction stability and good water resistance ability. The mechanism of the formaldehyde oxidation reaction is that formaldehyde is first oxidized to a dioxymethylene (DOM) intermediate and DOM dehydrogenation reaction is responsible for the formation of formate species (HCOO-).

Oyster shell-derived CuFe2O4-Hap nanocomposite for healthy houses: Bacterial and formaldehyde elimination

Bacterial infections and the threat of volatile organic compounds (VOCs) to human beings have attracted increasing concerns over the years. The simultaneous and effective eradication of bacteria while purifying indoor air has become an urgent issue. Herein, a biomass-based CuFe2O4-Hap was prepared via an ion-exchange method by loading CuFe2O4 with flower-shaped hydroxyapatite (Hap) obtained from oyster shells. Based on the experimental results and theoretical basis, the introduction of CuFe2O4 reduced the work function of hydroxyapatite and inhibited the recombination of photogenerated carriers. After irradiated for 15 min (300 W xenon lamp), the CuFe2O4-Hap photocatalysts exhibited excellent antibacterial efficiencies against Staphylococcus aureus (99.6 ± 0.35) % and Escherichia coli (99.7 ± 0.23) %, respectively. In addition, the functional coating prepared with CuFe2O4-Hap as the active material exhibited approximately 100 % HCHO conversion rate within 10 min under the full-spectrum light irradiation. The excellent photocatalytic decomposition performance could be attributed to the large specific surface area of nano-flower-shaped hydroxyapatite and the fast separation efficiency of photogenerated carriers. Overall, the proposed strategy is expected to stimulate further research into the biomass valorization for a healthier and environment-friendly lifestyle.

Regulating the electronic structure of Ir single atoms by ZrO2 nanoparticles for enhanced catalytic oxidation of formaldehyde at room temperature

Developing low-loading single-atom catalysts with superior catalytic activity and selectivity in formaldehyde (HCHO) oxidation at room temperature remains challenging. Herein, ZrO2 nanoparticles coupled low-loading Ir single atoms in N-doped carbon (Ir1-N-C/ZrO2) was prepared. The optimal Ir1-N-C/ZrO2 with 0.25 wt% Ir loading delivers the high HCHO removal and conversion efficiency (>95%) at 20 °C, which is higher than that over Ir1-N-C with the same Ir loading. The specific rate can reach 1285.6 mmol gIr−1 h−1, surpassing the Ir based catalysts reported to date. Density functional theory calculation results and electron spin resonance spectra indicate that the introduction of ZrO2 nanoparticles modulate the electronic structure of the Ir single atoms, promoting O2 activation to •O2–. Moreover, the Ir-C-Zr channel is favorable for the dissociation of •O2– to active oxygen atom (*O), and further accelerates the transformation of HCHO and intermediates (dioxymethylene and formates) to CO2 and H2O. This work provides a facile strategy to design low-loading single-atom catalysts with high catalytic activity toward HCHO oxidation.

MnO2 film promoted plasma-catalytic oxidation of HCHO and the identified active species on tubular ionizer

Tubular ionizers are dielectric barrier discharge devices widely employed for indoor air purification. Nonetheless, their practical application is limited by low efficiency and high concentrations of harmful by-products, such as ozone. To address these challenges, we have developed a new approach to integrate tubular ionizers with catalysts by uniformly spraying MnO2 catalysts onto the tubular medium. This synergistic coupling of plasma and catalysis significantly enhances the catalytic performance, leading to near twofold increase in the conversion of HCHO, while reducing ozone concentrations to two-thirds of those in the plasma-only system. We have also developed a fluorescence probe to detect the presence of free radicals such as HO• and O2−•. Our results demonstrate that the catalyst loading generates more hydroxyl and superoxide radicals, leading to superior catalytic performance.

Mn/HZSM-5 catalyst with high content of Mn4+ and surface hydroxyls for formaldehyde oxidation at room temperature

Catalytic oxidation of gaseous formaldehyde at room temperature over non-noble metal catalysts has wide application prospect. Regulation of catalyst surface active species such as surface hydroxyls, valence state of active metal, oxygen vacancies, etc., is effective in promoting catalytic performance. Herein, we prepared a series of Mn/HZSM-5 catalysts with a facile ball mill strategy. The optimal catalyst 0.4%Mn/HZSM-5 exhibited superior activity of nearly 100% HCHO conversion at 30 °C under 100 ppm gaseous HCHO condition. The characterization results revealed that the catalyst with high specific surface area has a large number of Mn4+ ions and hydroxyls on surface, which facilitates providing more active sites for formaldehyde oxidation. Combining XPS and chemisorption experiments, it was clear that the interaction between Mn4+ and the carriers provided more surface reactive oxygen species. In addition, in situ DRIFTS results revealed that Mn4+ and hydroxyls could jointly activate formaldehyde, and Mn4+ could further activate oxygen to oxidize the reaction intermediate to CO2 and H2O.

Single-Atom Cationic Ag and Metallic Ag Nanoparticles Supported on Al2O3 as Catalysts for Water-Resistant and CO2-Selective HCHO Oxidation

Ag-based catalysts have been extensively investigated in HCHO oxidation on account of the low price of the Ag precursor and their considerable low-temperature activity. It is known that H2 pretreatment has a remarkable promotion effect on Pt- and Pd- catalysts for HCHO oxidation, whereas the effect of H2 reduction on Ag-based catalysts has been rarely reported, probably due to the coexistence of multiple states of Ag species resulting from the high Ag loading. Herein, we prepared a 1% Ag/Al2O3 (Ag/Al-fresh) catalyst with Ag species in a uniform state and then reduced Ag/Al-fresh with H2 at 600 °C to obtain the Ag/Al-600H2 catalyst. We observed that H2 reduction had a significant influence on the performance of Ag/Al2O3 nanocatalysts in HCHO oxidation. In a dry reaction atmosphere, Ag/Al-fresh and Ag/Al-600H2 exhibited comparable HCHO conversion levels, but Ag/Al-600H2 showed much higher CO2 selectivity than Ag/Al-fresh. The presence of water vapor severely suppressed the HCHO conversion of the Ag/Al-fresh catalyst, while Ag/Al-600H2 showed high water resistance, maintaining high HCHO conversion and CO2 selectivity at 35% RH. Characterization results showed that the Ag species on Ag/Al-fresh and Ag/Al-600H2 were single-atom cationic Ag and metallic Ag nanoparticles, respectively. It was revealed that the Ag0 nanoparticles were more conducive than single-atom Ag+ to formate decomposition, as well as O2 and H2O activation, thus accelerating the conversion of HCOO– and CO intermediates to CO2 and contributing to the higher activity and water resistance of the Ag/Al-600H2 catalyst.

Efficient and cost-effective electrocatalytic CO2 to CO reduction over Sn-modified Cu nanowires by pairing with selective HCHO to HCOOH oxidation

Electrocatalytic CO2 reduction reaction (CO2RR) over Cu-based electrocatalysts still suffered from low efficiency but high energy consumption. In this study, atomic-dispersed Sn-modified Cu nanowires (Cu@Sn NWs) were synthesized for selective electrocatalytic CO2RR to CO with an optimized FECO of 96.4 %. Moreover, formaldehyde oxidation half-reaction (FOR) at MnO2/CP anode, replacing water oxidation (WOR), was introduced to build a novel CO2RR/FOR system with CO2RR over Cu@Sn NWs, to further improve CO2RR efficiency and to reduce the energy consumption. Generally, compared with CO2RR/WOR system, CO2RR/FOR system shows a much higher CO2RR performance. Meanwhile, HCHO can be converted to HCOOH at MnO2/CP anode with tunable selectivity (50 ∼ 65 %), depending on the applied cell voltage. Specifically, at a cell voltage of 3.5 V, about 97.9 % of HCHO can be removed with HCHO→HCOOH selectivity of about 50 %. Moreover, the working cell voltage and energy consumption can be significantly reduced over CO2RR/FOR system, versus CO2RR/WOR system. For example, at the current density of − 4 mA/cm2 (FECO = ∼95 %), the cell voltage is lower by about 270 mV, and the energy consumption is lower by about 8.97 %. Compared with the sum of the energy consumption of a single CO2RR and FOR, the energy consumption of the CO2RR/FOR system can be reduced by about 47.3 %. When solar cells were used as the power supply, the CO generation rate in the CO2RR/FOR system is about 1.43 times that in the CO2RR/WOR system, accompanied by the anodic conversion of HCHO to HCOOH with the selectivity of 58.2 %.

Metal-anchoring, metal oxidation-resistance, and electron transfer behavior of oxygen vacancy-rich TiO2 in supported noble metal catalyst for room temperature HCHO conversion

Thermal catalytic oxidation at room temperature using a noble metal catalyst is a rapid, stable, and efficient removal strategy for HCHO, a ubiquitous indoor air pollutant. However, the catalytic oxidation optimization through the support defect control has been barely explored. We prepared an oxygen vacancy-rich anatase TiO2 (VO-TiO2) as electron transfer catalyst support for the efficient catalytic conversion of HCHO to CO2 and H2O. VO-TiO2, prepared by chemical vapor condensation with post heat treatment, exhibits void-embedded nanostructures and electron paramagnetic activity, which governs the deposition pattern of Pt nanoparticles upon the impregnation. Pt/VO-TiO2 (0.086 wt% Pt) converted 100% of 10 ppm HCHO at room temperature and 200,000 cm3 h−1 gcat−1 GHSV in >250 min. The X-ray absorption (XAS) studies of used catalysts confirmed the conservation of metallic state of Pt only in oxygen vacancy-rich anatase TiO2 (VO-TiO2). The First-principles density-functional theory calculations revealed that the excess electrons at the oxygen vacancies in VO-TiO2 stabilize the otherwise-vulnerable Pt nanoparticles. This study demonstrates an effective defect control strategy for transforming a TiO2 support into a dynamic electron transfer catalyst platform.

Construction of α-MnO2/g-C3N4 Z-scheme heterojunction for photothermal synergistic catalytic decomposition of formaldehyde

Formaldehyde (HCHO), as the most common indoor air pollutant, undoubtedly poses a huge threat to people's health. It is of practical importance to achieve complete decomposition of HCHO to harmless CO2 at room temperature. Herein, α-MnO2/g-C3N4 Z-scheme heterojunction was constructed through the in-situ growth of α-MnO2 nanowires on the surface of g-C3N4 nanosheets. Owing to the construction of Z-scheme heterojunction, α-MnO2/g-C3N4 composite exhibits excellent photothermal catalytic activity, achieving complete mineralization of HCHO with the illumination of 191 mW/cm2 solar-light at GHSV of 180 L/gcat·h. Particularly, even under one sun and visible light radiation, the α-MnO2/g-C3N4 composite can still maintain 60% and 68% HCHO conversion, respectively. The formation of α-MnO2/g-C3N4 Z-scheme heterojunction not only effectively inhibits the photogenerated electron-hole pairs recombination, but also overcomes the band defects of the individual component. Furthermore, the mechanism of the photothermal catalysis of α-MnO2/g-C3N4 composite was discovered to be thermal-assisted photocatalytic process rather than solar-light driven thermalcatalysis. On the one hand, the thermal energy generated from light radiation can accelerate the migration of photo-generated carriers and improve the separation efficiency of photogenerated electrons from vacancies; on the other hand, it can decrease the activation energy of lattice oxygen and produce more surface-active oxygen species. This work provides cost-effective strategies and suggestions for decomposing HCHO and other VOCs in indoor air at room temperature.

HCHO oxidation over the δ-MnO2 catalyst: Enhancing oxidative activities of surface lattice oxygen and surface adsorbed oxygen by weakening Mn-O bond

The usages of HCHO in construction and decoration materials lead to serious indoor air pollution, removing the indoor HCHO to improve air quality is urgently required. In this work, we developed a new procedure to synthesis ultra-thin nanosheet δ-MnO2 without using traditional templates. The Mn-O bond was much weaker in the ultra-thin nanosheet δ-MnO2 than those in the β- and γ-MnO2. As a consequence, surface oxygen lattice of the δ-MnO2 was the most removable, generating the most oxygen vacancy on the surface. The oxidative ability of the lattice oxygen was the most enhanced, active surface adsorbed oxygen species were the most present on the δ-MnO2 surface. These contributed to an unexpected performance that 100 ppm HCHO was fully oxidized at 35–45 °C depending on the relative humidity between 10 and 50% at high space velocity of 300 L/(gh). When compared with HCHO oxidation performance of MnO2 in literatures, the current ultra-thin nanosheet δ-MnO2 lists the most active HCHO oxidation catalyst as regards to the lowest activation energy, the lowest temperature of full HCHO conversion and the highest rate of HCHO oxidation, giving the most promising potential application for practical indoor HCHO elimination.

One-step hydrothermal synthesis of Bi2WxMo1-xO6 solid solution with adjustable energy band coupling with g-C3N4: 2D/2D Z-scheme heterojunction for enhanced photocatalytic HCHO degradation under indoor conditions

In this work, 2D/2D Bi2WxMo1-xO6/g-C3N4 was synthesized via surfactant-assisted one-step hydrothermal method for the degradation of formaldehyde in simulated room environment. We utilized CTAC as surfactant to control the morphologies of Bi2WxMo1-xO6 coupling with g-C3N4 nanosheets. In the hydrothermal method, Mo replaced W to form solid solution which could reduce energy band gap of Bi2WO6. In contrast to Bi2W0.6Mo0.4O6 (43.1%) and g-C3N4 (23.2%), Bi2W0.6Mo0.4O6/g-C3N4 exhibited superior activity (92.4%) of photocatalytic degradation for formaldehyde at the initial concentration of 1 ppm under the relative humidity (RH) of 20%. Meanwhile, we simulated diverse typical indoor conditions to evaluate the applicability of catalysts. More importantly, Bi2W0.6Mo0.4O6/g-C3N4 performed satisfactory stability with 5.5% decrease in degradation efficiency after five cycles. The mechanism of enhanced HCHO conversion was ascribed to the formation of 2D/2D Z-scheme heterojunction between Bi2W0.6Mo0.4O6 and g-C3N4 which increased the accessible interface and promoted the separation of photo-generated carriers for oxidation of formaldehyde.

Calcium silicate hydrate decorated by Fe, Ti co-modified birnessite direct multi-component photocatalyst: Design, preparation and photocatalytic performance under visible light irradiation

Constructing a multi-component structure is an effective strategy to promote the formation of oxygen vacancies (OVs), which can enhance electron transition to improve the photocatalytic activity of materials. In this work, it was designed a series of novel photocatalysts supported on calcium silicate hydrates (C-S-H) via density functional theory calculation. These designed photocatalysts were then synthesized and marked as Bir@C-S-H, TiO2/Bir@C-S-H, and α-Fe2O3/TiO2/Bir@C-S-H, respectively. In comparison to other catalysts, α-Fe2O3/TiO2/Bir@C-S-H photocatalyst has a higher specific surface area, a lower band gap, more OVs, which can activate more dioxygen molecules, and more reactive radicals. The photocatalytic activity of as-synthesized photocatalysts was verified by using HCHO as the target pollutant. To the treatment of 80 ppm HCHO, the α-Fe2O3/TiO2/Bir@C-S-H exhibits 100% HCHO conversion corresponding gas hourly space velocity of 60 L/(g•h) with a relative humidity of 60% under visible light irradiation, while Bir@C-S-H and TiO2/Bir@C-S-H present 89.92% and 94.17% HCHO conversion, respectively at same conditions. This work demonstrates a more effective calcium silicate hydrate decorated by Fe, Ti co-modified birnessite heterostructures for HCHO oxidation, which can be directly used as decorative materials, providing a novel guidance for practical application.

Boosting the catalytic performance of Pt/TiO2 catalysts in room-temperature formaldehyde elimination by incorporating CeO2 promoters

To tackle the health threats caused by formaldehyde (HCHO) contamination, great efforts have been made to create high-performance and cost-efficiency catalysts that can completely remove HCHO at room temperature. Herein, we demonstrate an interface engineering strategy to improve the catalytic performance of Pt/TiO2 by introducing CeO2 promoters. When evaluated as catalysts in HCHO elimination reaction, the obtained 0.2Pt/5Ce-TiO2 catalysts possess remarkable catalytic activity and stability, which can completely convert 100 ppm HCHO into CO2 and H2O under a gas hourly space velocity of 120,000 mL gcat−1 h−1 at room temperature, and retain nearly 100% HCHO conversion after 28-h continuous test. Further structure-performance investigations reveal the crucial role of CeO2 that can significantly increase the contents of surface oxygen vacancies and Pt0 species, thereby the key intermediates including dioxymethylene, formate, and carbonate species can be easily converted. More importantly, the 0.2Pt/5Ce-TiO2 is readily sprayed onto the meltblown fabrics to construct an available face mask for protecting people against HCHO pollution, which can instantly remove 2.6 ∼ 4.0 ppm HCHO at room temperature, indicating the great potential in practical applications.