A Nonoxide Catalyst System Study: Alkali Metal-Promoted Pt/AC Catalyst for Formaldehyde Oxidation at Ambient Temperature

Unravelling High Water Vapor-Induced Inhibitory Effects on Pt/Co3O4 Catalysts toward Benzene Oxidation

Water vapor inevitably exists in the environment, which causes adverse impacts on many crucial chemical reactions. However, high water vapor of up to 10 vol %─relevant to a broad spectrum of industrial practices-for catalytic implications has been less investigated or neglected. As such, we explored an industry-relevant, humidity-highly sensitive benzene oxidation only in the presence of 10 vol % water vapor using the well-established Pt/Co3O4 catalysts, to bring such an important yet ignored topic to the forefront. Results revealed that Pt/Co3O4 catalysts possessing higher contents of Pt nanoparticles exhibited marked tolerance to water vapor interference. Under an incomplete benzene conversion condition, the input of 10 vol % water vapor indeed impaired the catalytic performance of Pt/Co3O4 catalyst significantly, which, in fact, was caused by the unfavorable formation of carboxylate species covering the catalyst's surface engendering irrecoverable activity loss, instead of the well-accepted water competitive adsorption. While such activity loss can be restored by elevating the reaction to a higher temperature. This study helps us to understand the compromised catalytic activity caused by high humidity, urging the systematic evaluation of well-established catalyst systems in high water vapor-contained conditions and pressing the development of water-tolerant catalysts for real-life application consideration.

Highly exposed metal atomic active sites in Al2O3/CoNC: Modify reaction pathways by coupling oxygen species

The catalytic oxidation of formaldehyde (HCHO) at ambient temperature is a highly efficient, cost-effective and environmentally friendly approach for formaldehyde removal. Reactive oxygen (O*) and reactive hydroxyl groups (OH*) are the main active species in the catalytic oxidation reaction of HCHO. Therefore, it is crucial to design catalysts that can simultaneously enhance the surface concentrations of O* and OH*, thereby improving their overall catalytic performance. The present study aimed to design an Al2O3/CoNC catalyst featuring layered carbon nitride coupled with metal oxides possessing domain-limited cobalt (Co) metal active sites, to efficiently remove HCHO (≈100 %, 100 ppm, RH=50 %, GSHV=20,000 mL/(g h)) and ensure stability (more than 90 % formaldehyde removal within 450 h) at ambient temperature. The characterization revealed that the interaction between Al2O3-supported metal and CoNC resulted in enhanced confinement of Co, leading to a higher abundance of edge structures exposing more active sites. Additionally, the presence of highly dispersed Co-NX active sites and increased oxygen vacancies effectively facilitated the adsorption and activation processes of HCHO and O2, as well as the adsorption and desorption dynamics of intermediates during the reaction. These factors collectively contributed to an improved catalytic activity. The results of in situ infrared spectroscopy revealed that the catalyst improved the adsorption and activation of O2 and H2O, leading to the rapid generation of substantial amounts of O* and OH*. This synergistic interaction between Al2O3 and CoNC plays a crucial role in the sustained production of O* and OH*, promoting efficient of intermediate decomposition, and ensuring excellent catalytic activity and stability for HCHO.

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.

Efficient and Durable Oxidation Removal of Formaldehyde over Layered Double Hydroxide Catalysts at Room Temperature

Room temperature catalytic oxidation (RTCO) using non-noble metals has emerged as a highly promising technique for removal of formaldehyde (HCHO) under ambient conditions; however, non-noble catalysts still face the challenges related to poor water resistance and low stability under harsh conditions. In this study, we synthesized a series of layered double hydroxides (LDHs) incorporating various dual metals (MgAl, ZnAl, NiAl, NiFe, and NiTi) for formaldehyde oxidation at ambient temperature. Among the synthesized catalysts, the NiTi-LDH catalyst showed an HCHO removal efficiency and CO2 yield close to 100.0%, and exceptional water resistance and chemical stability on running 1300 min. The abundant hydroxyl groups in LDHs directly bonded with HCHO, leading to the production of CO2 and H2O, thus inhibiting the formation of CO, even in the absence of O2 and H2O. The coexistence of O2 effectively reduced the reaction barrier for H2O molecule dissociation, facilitating the formation of hydroxyl groups and their subsequent backfill on the catalyst surface. The mechanisms underlying the involvement and regeneration of hydroxyl groups in room temperature oxidation of formaldehyde were elucidated with the combined in situ DRIFTS, HCHO-TPD-MS, and DFT calculations. This work not only demonstrates the potential of LDH catalysts in environmental applications but also advances the understanding of the fundamental processes involved in room temperature oxidation of formaldehyde.

Catalytic Oxidation of Benzene over Atomic Active Site AgNi/BCN Catalysts at Room Temperature

Benzene is the typical volatile organic compound (VOC) of indoor and outdoor air pollution, which harms human health and the environment. Due to the stability of their aromatic structure, the catalytic oxidation of benzene rings in an environment without an external energy input is difficult. In this study, the efficient degradation of benzene at room temperature was achieved by constructing Ag and Ni bimetallic active site catalysts (AgNi/BCN) supported on boron-carbon-nitrogen aerogel. The atomic-scale Ag and Ni are uniformly dispersed on the catalyst surface and form Ag/Ni-C/N bonds with C and N, which were conducive to the catalytic oxidation of benzene at room temperature. Further catalytic reaction mechanisms indicate that benzene reacted with ·OH to produce R·, which reacted with O2 to regenerate ·OH. Under the strong oxidation of ·OH, benzene was oxidized to form alcohols, carboxylic acids, and eventually CO2 and H2O. This study not only significantly reduces the energy consumption of VOC catalytic oxidation, but also improves the safety of VOC treatment, providing new ideas for the low energy consumption and green development of VOC treatment.

Formaldehyde Ambient-Temperature Decomposition over Pd/Mn3O4-MnO Driven by Active Sites' Self-Tandem Catalysis

The widespread presence of formaldehyde (HCHO) pollutant has aroused significant environmental and health concerns. The catalytic oxidation of HCHO into CO2 and H2O at ambient temperature is regarded as one of the most efficacious and environmentally friendly approaches; to achieve this, however, accelerating the intermediate formate species formation and decomposition remains an ongoing obstacle. Herein, a unique tandem catalytic system with outstanding performance in low-temperature HCHO oxidation is proposed on well-structured Pd/Mn3O4-MnO catalysts possessing bifunctional catalytic centers. Notably, the optimized tandem catalyst achieves complete oxidation of 100 ppm of HCHO at just 18 °C, much better than the Pd/Mn3O4 (30%) and Pd/MnO (27%) counterparts as well as other physical tandem catalysts. The operando analyses and physical tandem investigations reveal that HCHO is primarily activated to gaseous HCOOH on the surface of Pd/Mn3O4 and subsequently converted to H2CO3 on the Pd/MnO component for deep decomposition. Theoretical studies disclose that Pd/Mn3O4 exhibits a favorable reaction energy barrier for the HCHO → HCOOH step compared to Pd/MnO; while conversely, the HCOOH → H2CO3 step is more facilely accomplished over Pd/MnO. Furthermore, the nanoscale intimacy between two components enhances the mobility of lattice oxygen, thereby facilitating interfacial reconstruction and promoting interaction between active sites of Pd/Mn3O4 and Pd/MnO in local vicinity, which further benefits sustained HCHO tandem catalytic oxidation. The tandem catalysis demonstrated in this work provides a generalizable platform for the future design of well-defined functional catalysts for oxidation reactions.

Defect-Confinement Strategy for Constructing CuO Clusters on Carbon Nanotubes for Catalytic Oxidation of AsH3 at Room Temperature

The efficient removal of the highly toxic arsine gas (AsH3) from industrial tail gases under mild conditions remains a formidable challenge. In this study, we utilized the confinement effect of defective carbon nanotubes to fabricate a CuO cluster catalyst (CuO/ACNT), which exhibited a capacity much higher than that of CuO supported on pristine multiwalled carbon nanotubes (MWCNT) (CuO/PCNT) for catalytically oxidizing AsH3 under ambient conditions. The experimental and theoretical results show that nitric acid steam treatment could induce MWCNT surface structural defects, which facilitated more stable anchoring of CuO and then improved the oxygen activation ability, therefore leading to excellent catalytic performance. Density functional theory (DFT) calculations revealed that the catalytic oxidation of AsH3 proceeded through stepwise dehydrogenation and subsequent recombination with oxygen to form As2O3 as the final product.

Hydroxyl-Decorated Pt as a Robust Water-Resistant Catalyst for Catalytic Benzene Oxidation

In catalytic oxidation reactions, the presence of environmental water poses challenges to the performance of Pt catalysts. This study aims to overcome this challenge by introducing hydroxyl groups onto the surface of Pt catalysts using the pyrolysis reduction method. Two silica supports were employed to investigate the impact of hydroxyl groups: SiO2-OH with hydroxyl groups and SiO2-C without hydroxyl groups. Structural characterization confirmed the presence of Pt-Ox, Pt-OHx, and Pt0 species in the Pt/SiO2-OH catalysts, while only Pt-Ox and Pt0 species were observed in the Pt/SiO2-C catalysts. Catalytic performance tests demonstrated the remarkable capacity of the 0.5 wt % Pt/SiO2-OH catalyst, achieving complete conversion of benzene at 160 °C under a high space velocity of 60,000 h-1. Notably, the catalytic oxidation capacity of the Pt/SiO2-OH catalyst remained largely unaffected even in the presence of 10 vol % water vapor. Moreover, the catalyst exhibited exceptional recyclability and stability, maintaining its performance over 16 repeated cycles and a continuous operation time of 70 h. Theoretical calculations revealed that the construction of Pt-OHx sites on the catalyst surface was beneficial for modulating the d-band structure, which in turn enhanced the adsorption and activation of reactants. This finding highlights the efficacy of decorating the Pt surface with hydroxyl groups as an effective strategy for improving the water resistance, catalytic activity, and long-term stability of Pt catalysts.

Attachment of facile synthesized NaCo2O4 nanodots to SiO2 nanoflakes for sodium-rich boosted Pt-dominated ambient HCHO oxidation

Surface alkali metal ions are typically utilized as available promoters for ambient HCHO oxidation. In this study, NaCo₂O₄ nanodots with two different preferential crystallographic orientations are synthesized by facile attachment to SiO₂ nanoflakes with varying degrees of lattice defects. A unique Na-rich environment is established through interlayer Na⁺ diffusion based on the small size effect. The optimized catalyst Pt/HNaCo₂O₄/T₂ can deal with HCHO below 5 ppm in the static measurement system with a sustained release background and produces approximately 40 ppm of CO₂ in 2 h. Combining the experimental analyses with density functional theory (DFT) calculations, the possible catalytic enhancing mechanism is proposed from the support promotion perspective, and the positive synergistic effect of Na-rich, oxygen vacancies and optimized facets for Pt-dominant ambient HCHO oxidation via both kinetic and thermodynamic processes is confirmed.

Regulating the Pt1-CeO2 interaction via alkali modification for boosting the catalytic performance of single-atom catalysts

With the introduction of potassium species, the catalytic oxidation performance over the Pt₁/CeO₂ catalyst was significantly enhanced, where potassium ions acted as structural and electronic promoters, and formed Pt-O-K interactions with Pt to directly regulate the coordination environment and electronic state of Pt and the metal-support interaction between Pt and CeO₂.

Bimetallic oxide Cu2O@MnO2 with exposed phase interfaces for dual-effect purification of indoor formaldehyde and pathogenic bacteria

The combination of materials with different functions is an optimal strategy for synchronously removing various indoor pollutants. For multiphase composites, exposing all components and their phase interfaces fully to the reaction atmosphere is a critical problem that needs to be solved urgently. Here, a bimetallic oxide Cu2O@MnO2 with exposed phase interfaces was prepared by a surfactant-assisted two-step electrochemical method, which shows a composite structure of non-continuously dispersed Cu2O particles anchored on flower-like MnO2. Compared with the pure catalyst MnO2 and bacteriostatic agent Cu2O, Cu2O@MnO2 respectively shows superior dynamic formaldehyde (HCHO) removal efficiency (97.2% with a weight hourly space velocity of 120 000 mL g-1 h-1) and pathogen inactivation ability (the minimum inhibitory concentration for 104 CFU mL-1 Staphylococcus aureus is 10 μg mL-1). According to material characterization and theoretical calculation, its excellent catalytic-oxidative activity is attributable to the electron-rich region at the phase interface which is fully exposed to the reaction atmosphere, inducing the capture and activation of O2 on the material surface, and then promoting the generation of reactive oxygen species that can be used for the oxidative-removal of HCHO and bacteria. Additionally, as a photocatalytic semiconductor, Cu2O further enhances the catalytic ability of Cu2O@MnO2 under the assistance of visible light. This work will provide efficient theoretical guidance and a practical basis for the ingenious construction of multiphase coexisting composites in the field of multi-functional indoor pollutant purification strategies.

Construction of strongly-coupled CeO2/MnO2 heterogeneous catalysts for highly-efficient removal of formaldehyde

Formaldehyde (HCHO) is highly toxic, but its low-temperature elimination is still a pressing challenge nowadays.

Low Loading and High Activity of Platinum Oxide Nanoclusters Formed by Defect Engineering of a Metal-Organic Framework for Formaldehyde Degradation

A distinct platinum oxide nanocluster (PtO_x ) was developed, consisting of only Pt-O bond by a defect-engineered Al metal-organic framework (MOF) (BIT-72) with superior formaldehyde (HCHO) degradation activity and stability. With only 0.015 wt % Pt loading, PtO_x @BIT-72-DE could degrade HCHO with 100 % conversion continuously for at least 200 h under HCHO concentration of 25 ppm and gas hourly space velocity of 60000 mL g^-1  h^-1 at room temperature. Furthermore, its specific rate (446 mmol_HCHO  g_Pt ^-1  h^-1 ) was higher than for traditional Pt-based catalysts and single-atom Pt catalysts. Moreover, the cost of PtO_x @BIT-72-DE was lowered to 0.0769 $ g^-1 , which could significantly facilitate its commercial application. This study demonstrates the promising potential of MOFs in the design of HCHO degradation catalysts.

Assembled Organoruthenium(II) for Formaldehyde Decomposition and Hydrogen Production

Formaldehyde decomposition is not only an attractive method for hydrogen production, but also a potential approach for gaseous formaldehyde removal. In this research, we prepare some assembled organoruthenium through coordination reaction between Ru(p-Cymene)Cl₂ and bridge-linking ligands. It is a creative approach for Ru(p-Cymene)Cl₂ conversion into heterogeneous particles. The rigidity of bridge-linking ligand enables assembled organoruthenium to have highly ordered crystalline structure, even show clear crystal lattice with spacing of 0.19 nm. XPS shows the N-Ru bond are formed between bridge-linking ligand and Ru(p-Cymene)Cl₂ . The assembled organoruthenium has high abundant active sites for formaldehyde decomposition at low temperature. The reaction rate could increase linearly with temperature and formaldehyde concentration, with a TOF of 2420 h^-1 at 90 °C. It is promising for gaseous formaldehyde decomposition in wet air or nitrogen. Formaldehyde conversion is up to 95 % over Ru-DAPM is 4,4'-diaminodiphenylmethane at 90 °C in air. Gaseous formaldehyde decomposition is a two-steps process under oxygen-free condition. Firstly, formaldehyde dissolve in water, and be converted into hydrogen and formic acid through formaldehyde-water shift reaction. Then intermediate formic acid will further decompose into hydrogen and carbon dioxide. We also find formaldehyde decomposition is a synergetic catalysis process of oxygen and water in moist air. Oxygen is conducive to formic acid desorption and decomposition on the active sites, so assembled organoruthenium exhibit slightly higher conversion for formaldehyde decomposition in moist air. This work proposes a distinctive method for gaseous formaldehyde decomposition in the air, which is entirely different from formaldehyde photocatalysis or thermocatalysis oxidation.

Acid-Modified Sepiolite-Supported Pt (Noble Metal) Catalysts for HCHO Oxidation at Ambient Temperature

The critical need to enhance the quality of indoor air leads to the improvement of catalyst activity for the removal of formaldehyde. Sepiolite can be utilized in catalytic reactions for its unique structure, composition and high surface area. The adhesion between sepiolite fibers and the blocked microporous channel (by impurities) demands the activation of natural sepiolite through acid treatment. This treatment successfully produces acid-modified sepiolite Pt-supported samples. The impacts of different acid concentrations, Pt loading content and calcination temperature on catalytic activity for formaldehyde (HCHO) oxidation are studied. The catalytic activity of HCHO is characterized and evaluated by techniques including specific surface area, X-ray diffraction, Fourier transform infrared spectrum, X-ray photoelectron spectroscopy and transmission electron microscopy. The results show the maximum specific area of sepiolite at the optimized 0.06 M acid concentration. Among all the prepared samples, the 0.02Pt/Sep catalyst calcined at 500 °C exhibits the highest catalytic activity for the oxidation of HCHO.

A qualitative exploratory study on the effects of formalin on mortuary attendants

Objectives:

To explore the effects of formalin on mortuary attendants in nine selected hospitals in Ghana.

Methods:

The study applies a qualitative exploratory descriptive design in the overall collection and analysis of data. Purposive sampling was used to reach the saturation of 19 participants. The data were collected through semi-structured interviews and manually analysed using content analysis.

Results:

Five themes developed from the analysed data, namely, effects of formalin on the eyes, effects of formalin on the respiratory system, effects of formalin on the skin, effects on appetite, and formalin as a cancer-causing agent.

Conclusion:

This study has unveiled the negative effects of formalin on morgue attendants, which is likely to cause long-time health problems. It is therefore recommended that all mortuaries in Ghana should be assisted with protective equipment, in-service training, and practice of universal safety to help reduce risks associated with chemical hazards, especially formalin. There should be regular surveillance in the mortuaries and workers be screened regularly.

Controllable synthesis of magic cube-like Ce-MOF-derived Pt/CeO2 catalysts for formaldehyde oxidation

Controllable synthesis of MOFs with desired structures is of great significance to deepen the understanding of the crystal nucleation-growth mechanism and deliver unique structural features to their derived metal oxides with target catalytic applications. In this study, NH₂-Ce-BDC with morphology similar to a second-order magic cube (mc) is facile synthesized via H⁺ mediation in nucleation and growth stages. The pertinent variables that can greatly influence the formation of magic cube-like structures (MCS) were investigated, in which the concentric diffusion field was found to be one of the key factors. Upon calcination, the derived CeO₂ inherits unique gullies and grooves located on the pristine MOFs surface, which is quite useful for atomic layer deposition (ALD) of platinum (Pt) nanoparticles because of strong interaction with MOF-derived CeO₂ (mc-CeO₂). XPS, H₂-TPR, Raman, and in situ DRIFTS characterization results show that there is a stronger interaction between Pt and mc-CeO₂ in mc-Pt/CeO₂ compared with c-Pt/CeO₂ that is derived from the well-developed cubic Ce-MOFs. Furthermore, Pt²⁺ ions, hydroxyl oxygen, and oxygen defects in mc-Pt/CeO₂ account highly for exemplary catalytic activity toward HCHO oxidation.

Enhanced the synergistic degradation effect between active hydroxyl and reactive oxygen species for indoor formaldehyde based on platinum atoms modified MnOOH/MnO2 catalyst

Maintaining high activity during prolonged catalysis is always the pursuit in catalytic degradation of organic pollutants. For indoor formaldehyde (HCHO) degradation, the accumulation of intermediates is the major factor limiting the conversion of HCHO to final product CO₂ (HCHO-to-CO₂ conversion) and long-lasting catalysis. Herein, a three-dimensional radialized nanostructure catalyst self-assembled by MnOOH/MnO₂ nanosheets anchored with Pt single atoms (Pt_SA-MnOOH/MnO₂ with a trace platinum loading amount of 0.09%) is developed by thermally assisted two-step electrochemical method, which achieves enhanced CO₂ production in catalytic HCHO degradation at the room temperature by the collaborative action of active hydroxyl (OH*) and active oxygen species (O₂*). By boosting intermediates' decomposing, the catalyst implements real-time HCHO-to-CO₂ conversion (∼85.7%) and long-term continuous HCHO removal (∼98%) during 100 h in a 15 ppm HCHO atmosphere at 25 °C under a weight hourly space velocity of 30000 mL/g_cat∙h. Density functional theory calculation shows that the formation energy of O₂* from O₂ over Pt_SA-MnOOH/MnO₂ is nearly half lower than that over Pt-MnO₂ catalyst. And decomposing accumulated intermediates gives the credit to OH* species sustainably generated by the combined action of MnOOH and O₂*. The synergistic action between Pt_SA and MnOOH contributes to the continuous production of O₂* and OH* for enhancing CO₂ production in indoor catalytic formaldehyde degradation.

Effect of Hydroxyl Groups on Metal Anchoring and Formaldehyde Oxidation Performance of Pt/Al2O3

Pt/Al₂O₃ catalysts showing excellent activity and stability have been used in various reactions, including HCHO oxidation. Herein, we prepared Pt-Na/Al₂O₃ catalysts with a Pt content of 0.05 wt % to reveal the key factors determining the anchoring of Pt as well as the catalytic activity and mechanism of HCHO oxidation. Pt-Na/nano-Al₂O₃ (denoted as Pt-Na/nAl₂O₃) catalysts with 0.05 wt % Pt content could completely oxidize HCHO to CO₂ at room temperature, which is the lowest Pt content used in HCHO catalytic oxidation to our knowledge. After Na addition, terminal hydroxyl groups (denoted as HO-μ_ter) on nano-Al₂O₃ were transformed to doubly bridging hydroxyl groups between Na and Al (denoted as HO-μ_bri(Na-Al)), which atomically dispersed Pt species. Pt anchoring further promoted the regeneration of HO-μ_bri(Na-Al) by activating O₂ and H₂O, oxidizing HCHO to CO₂ directly by the fast reaction step ([HCOO^-] + [OH]_a → CO₂ + H₂O). Our study revealed that the HO-μ_bri(Na-Al) synergistically generated by HO-μ_ter and Na species provided anchoring sites for Pt species.

Enhanced Formaldehyde Oxidation Performance of the Mesoporous TiO2(B)-Supported Pt Catalyst: The Role of Hydroxyls

As one of the crystal phases of titania, TiO₂(B) was first utilized as a catalyst carrier for the oxidation of formaldehyde (HCHO). The mesoporous TiO₂(B) loaded with Pt nanoparticles enhanced the HCHO oxidation reaction whose reaction rate was 4.5-8.4 times those of other crystalline TiO₂-supported Pt catalysts. Simultaneously, Pt/TiO₂(B) exhibited long-term stable HCHO oxidation performance. The structural characterization results showed that in comparison with Pt/anatase, Pt/TiO₂(B) had more abundant hydroxyls, facilitating increasing the content of oxygen species. Studies on the role of hydroxyls in HCHO oxidation of Pt/TiO₂(B) illustrated that synergistic involvement of terminally bound hydroxyls and bridging hydroxyls in HCHO oxidation accelerated the transformation from HCHO to formate via dioxymethylene. Moreover, hydroxyls could avoid the accumulation of excessive formate on Pt/TiO₂(B) and promote the rapid oxidation of CO. Accordingly, the hydroxyl groups could accelerate each substep of formaldehyde oxidation, which enabled Pt/TiO₂(B) to exhibit excellent formaldehyde oxidation performance.

Pt-Co nanoparticles supported on hollow multi-shelled CeO2 as a catalyst for highly efficient toluene oxidation: Morphology control and the role of bimetal synergism

A series of hollow multi-shelled CeO₂ (HoMS-CeO₂) support materials with tunable shell numbers were fabricated and applied to the catalytic oxidation of toluene. HoMS-CeO₂ possess much higher catalytic activity (T₉₀ = 236 ℃) than hollow CeO₂ with only a single shell (h-CeO₂) (T₉₀ = 275℃). The porous multiple-shelled structure has a higher S_BET, which strongly promotes gas distribution and provides more active sites. The superiority of this kind of structure was also verified by comparing h-Co₃O₄ and HoMS-Co₃O₄. Furthermore, Pt-Co bimetallic nanoparticles were loaded onto HoMS-CeO₂. The synergistic effect between Pt and Co was verified by XPS and O₂-TPD, which was observed to allow electron transfer between Pt and Co and thus regulate the electronic state of the Pt. Compared with Pt alone, Pt-Co bimetallic nanoparticles could stronglypromotethe activation of O₂and oxygen mobility, as revealed by a much higher O_ads content and a lower oxygen desorption temperature. Of the catalysts prepared in this study, the 1 wt% PtCo₃/CeO₂ catalyst was found to be the most suitable for toluene oxidation owing to its excellent activity (T₉₀ = 158 ℃), long-term stability, and water resistance. Finally, in situ DRIFTS was employed to investigate mechanism during toluene oxidation and the possible reaction pathway was proposed.

Acid pretreatment of support promotes Pd/SiO2 activity for formaldehyde oxidation at room temperature

Hydroxyl groups on SiO2 produced by acid pretreatment favored the anchoring of Pd particles and increased their dispersion, which induced more oxygen vacancies on the surface of catalysts and further enhanced H2O activation.

Water-induced gaseous formaldehyde decomposition using ruthenium organic crystalline particles

Novel ruthenium organic crystalline particles are prepared for providing two distinctive approaches for formaldehyde decomposition: catalytic oxidation or water-induced formaldehyde decomposition.

A simple method to regulate surface hydroxy groups on Al2O3 for improving catalytic oxidation performance for HCHO on Pt/Al2O3

For supported noble metal catalysts, the properties of the support had great influence on the state of noble metals. Herein, we chose Al2O3 as model to find a simple method...

Degradation of Formaldehyde over MnO2/CeO2 Hollow Spheres: Elucidating the Influence of Carbon Sphere Self-Sacrificing Templates

Here, we prepare a MnO₂/CeO₂ hollow sphere catalyst using the carbon sphere as a self-sacrificing template for formaldehyde (HCHO) removal. In the feed gas of 20 ppm of HCHO (balanced by N₂) + 20 vol % O₂, a HCHO removal efficiency of 70% was achieved at 20 °C and full conversion was reached at around 47 °C at GHSV = 50,000 mL (g_cat h)^-1 for MnO₂/CeO₂ hollow spheres. The catalytic performance and structural and chemical properties of MnO₂/CeO₂ hollow spheres for the removal of core carbon spheres were explored, and the influence of using the carbon sphere as a self-sacrificing template was proved by comparing with carbon@MnO₂/CeO₂ (a core carbon sphere with a MnO₂/CeO₂ shell) and nonmorphologic MnO₂/CeO₂. The properties of the MnO₂/CeO₂ hollow spheres are significantly improved compared to carbon@MnO₂/CeO₂ (removal efficiency of 45% at 150 °C) and MnO₂/CeO₂ (removal efficiency of 46% at 20 °C) as a result of an evolution in the interaction between Mn/Ce and carbon. This increase in the interaction strength seems to (i) increase the oxygen vacancy, (ii) promote the oxygen species mobility, and (iii) improve the chemical stability of the MnO₂/CeO₂ hollow spheres. We believe that these results are beneficial to the fabrication of binary transition metal oxides and applications of them in HCHO removal.

Surface Lattice Oxygen Activation by Nitrogen-Doped Manganese Dioxide as an Effective and Longevous Catalyst for Indoor HCHO Decomposition

Oxygen vacancy plays an important role in catalytic oxidation of formaldehyde (HCHO), but the inherent drawback of its thermodynamic instability causes the deactivation of catalysts. Hence, improving the thermodynamic stability of oxygen vacancy is a crux during HCHO oxidation. Here, a novel and simple nitrogen doping of MnO₂/C catalyst is designed for HCHO oxidation at room temperature. The surface lattice oxygen of MnO₂ will be activated by nitrogen-doping, which acts as active sites for HCHO oxidation and solves the thermodynamic instability issue of oxygen vacancy. Furthermore, carbon is doped with nitrogen to promote electron transfer and accelerate the HCHO oxidation process. Therefore, the catalytic activity and stability of the catalyst can be significantly promoted, which can completely remove ∼1 ppm HCHO in the tank within 3 h, and remains highly active after 5 cycles at room temperature (RH = 55%). In addition, the excellent removal performance over the prepared catalyst is also attributed to abundant surface oxygen species, amorphous crystallinity, and low reduction temperature. In situ diffuse reflectance infrared Fourier transform spectrometry (DRIFTS) and density functional theory (DFT) calculations reveal the reaction mechanism of HCHO. This strategy provides crucial enlightenment for designing novel Mn-based catalysts for application in the HCHO oxidation field.