Efficient removal of formaldehyde by nanosized gold on well-defined CeO₂ nanorods at room temperature

Pioneering superior efficiency in Methylene blue and Rhodamine b dye degradation under solar light irradiation using CeO2/Co3O4/g-C3N4 ternary photocatalysts

In this research work, we have successfully synthesized the CeO2/Co3O4/g-C3N4 ternary nanocomposite for hydrothermal method for photocatalytic applications. The synthesized nanocomposites were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy TEM, Photoluminescent spectra (PL), X-ray photoelectron spectroscopy (XPS), Brunauer- Emmett-Teller (BET) and Ultraviolet diffuse reflectance spectroscopy (UV-DRS) technique. As per the optical spectroscopic investigations CeO2/Co3O4/g-C3N4 ternary nanocomposite exhibited the high optical absorption range and its band gap is reduced from 2.95 eV to1.83 eV. The PL spectra showed the lowered emission peak intensity of ternary nanocomposite which is revealed that the better charge separation and slow recombination of electron hole pairs. The highest photocatalytic degradation efficiency of CeO2/Co3O4/g-C3N4 ternary nanocomposite showed 93 % and 86 % towards the pollutant methylene blue and Rhodamine B. Moreover, photodegradation of the pollutants followed pseudo-first order kinetics with a very high-rate constant of 0.02211 min-1 and 0.017756 min-1. Additionally, the ternary nano catalyst was delivered the remarkable stability performance even after five cycles. This research may provide a low-cost approach for synthesized visible light responsive catalysts for use in environmental remediation applications.

MOF-Derived Mn2 O3 Nanocage with Oxygen Vacancies as Efficient Cathode Catalysts for Li-O2 Batteries

Designing efficient and cost-effective electrocatalysts is the primary imperative for addressing the pivotal concerns confronting lithium-oxygen batteries (LOBs). The microstructure of the catalyst is one of the key factors that influence the catalytic performance. This study proceeds to the advantage of metal-organic frameworks (MOFs) derivatives by annealing manganese 1,2,3-triazolate (MET-2) at different temperatures to optimize Mn2 O3 crystals for special microstructures. It is found that at 350 °C annealing temperature, the derived Mn2 O3 nanocage maintains the structure of MOF, the inherited high porosity and large specific surface area provide more channels for Li+ and O2 diffusion, beside the oxygen vacancies on the surface of Mn2 O3 nanocages enhance the electrocatalytic activity. With the synergy of unique structure and rich oxygen vacancies, the Mn2 O3 nanocage exhibits ultrahigh discharge capacity (21 070.6 mAh g-1 at 500 mA g-1 ) and excellent cycling stability (180 cycles at the limited capacity of 600 mAh g-1 with a current of 500 mA g-1 ). This study demonstrates that the Mn2 O3 nanocage structure containing oxygen vacancies can significantly enhance catalytic performance for LOBs, which provide a simple method for structurally designed transition metal oxide electrocatalysts.

β-Cyclodextrin Stabilized Nanoceria for Hydrolytic Cleavage of Paraoxon in Aqueous and Cationic Micellar Media

Beta-cyclodextrin (β-CD) stabilized cerium oxide nanoparticles (β-CD@CeO₂ NPs) were synthesized through a hydrothermal route. The electronic properties, surface functional group, surface composition, size, and morphologies of the as-synthesized β-CD@CeO₂ NPs were characterized using UV-visible spectroscopy, FTIR analysis, high resolution X-ray photoelectron spectroscopy (HRXPS), high resolution transmission electron microscopy (HRTEM), and field emission scanning electron microscopy (FESEM). The pH-dependent variation of the ζ-potential of β-CD@CeO₂ NPs and the catalytic activity of the NPs for the hydrolysis of paraoxon were investigated. The observed pseudo-first-order rate constant (k_obs) for the hydrolysis of paraoxon is increased with increasing pH and the ζ-potential of β-CD@CeO₂ NPs. The kinetics and mechanism of hydrolysis of paraoxon in the aqueous and cationic micellar media have been discussed.

Effect of preparation method of noble metal supported catalyts on formaldehyde oxidation at room temperature: Gas or liquid phase reduction

Formaldehyde (HCHO) is toxic to the human body and is one of the main threats to the indoor air quality (IAQ). As such, the removal of HCHO is imperative to improving the IAQ, whereby the most useful method to effectively remove HCHO at room temperature is catalytic oxidation. This review discusses catalysts for HCHO room-temperature oxidation, which are categorized according to their preparation methods, i.e., gas-phase reduction and liquid-phase reduction methods. The HCHO oxidation performances, structural features, and reaction mechanisms of the different catalysts are discussed, and directions for future research on catalytic oxidation are reviewed.

Modification of Polymeric Carbon Nitride with Au-CeO2 Hybrids to Improve Photocatalytic Activity for Hydrogen Evolution

The construction of a multi-component heterostructure for promoting the exciton splitting and charge separation of conjugated polymer semiconductors has attracted increasing attention in view of improving their photocatalytic activity. Here, we integrated Au nanoparticles (NPs) decorated CeO2 (Au-CeO2) with polymeric carbon nitride (PCN) via a modified thermal polymerization method. The combination of the interfacial interaction between PCN and CeO2 via N-O or C-O bonds, with the interior electronic transmission channel built by the decoration of Au NPs at the interface between CeO2 and PCN, endows CeAu-CN with excellent efficiency in the transfer and separation of photo-induced carriers, leading to the enhancement of photochemical activity. The amount-optimized CeAu-CN nanocomposites are capable of producing ca. 80 μmol· H2 per hour under visible light irradiation, which is higher than that of pristine CN, Ce-CN and physical mixed CeAu and PCN systems. In addition, the photocatalytic activity of CeAu-CN remains unchanged for four runs in 4 h. The present work not only provides a sample and feasible strategy to synthesize highly efficient organic polymer composites containing metal-assisted heterojunction photocatalysts, but also opens up a new avenue for the rational design and synthesis of potentially efficient PCN-based materials for efficient hydrogen evolution.

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.

Designing Sites in Heterogeneous Catalysis: Are We Reaching Selectivities Competitive With Those of Homogeneous Catalysts?

A critical review of different prominent nanotechnologies adapted to catalysis is provided, with focus on how they contribute to the improvement of selectivity in heterogeneous catalysis. Ways to modify catalytic sites range from the use of the reversible or irreversible adsorption of molecular modifiers to the immobilization or tethering of homogeneous catalysts and the development of well-defined catalytic sites on solid surfaces. The latter covers methods for the dispersion of single-atom sites within solid supports as well as the use of complex nanostructures, and it includes the post-modification of materials via processes such as silylation and atomic layer deposition. All these methodologies exhibit both advantages and limitations, but all offer new avenues for the design of catalysts for specific applications. Because of the high cost of most nanotechnologies and the fact that the resulting materials may exhibit limited thermal or chemical stability, they may be best aimed at improving the selective synthesis of high value-added chemicals, to be incorporated in organic synthesis schemes, but other applications are being explored as well to address problems in energy production, for instance, and to design greener chemical processes. The details of each of these approaches are discussed, and representative examples are provided. We conclude with some general remarks on the future of this field.

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.

Ambient Air Purification by Nanotechnologies: From Theory to Application

Air pollution has been a recurring problem in northern Chinese cities, and high concentrations of PM2.5 in winter have been a particular cause for concern. Secondary aerosols converted from precursor gases (i.e., nitrogen oxides and volatile organic compounds) evidently account for a large fraction of the PM2.5. Conventional control methods, such as dust removal, desulfurization, and denitrification, help reduce emissions from stationary combustion sources, but these measures have not led to decreases in haze events. Recent advances in nanomaterials and nanotechnology provide new opportunities for removing fine particles and gaseous pollutants from ambient air and reducing the impacts on human health. This review begins with overviews of air pollution and traditional abatement technologies, and then advances in ambient air purification by nanotechnologies, including filtration, adsorption, photocatalysis, and ambient-temperature catalysis are presented—from fundamental principles to applications. Current state-of-the-art developments in the use of nanomaterials for particle removal, gas adsorption, and catalysis are summarized, and practical applications of catalysis-based techniques for air purification by nanomaterials in indoor, semi-enclosed, and open spaces are highlighted. Finally, we propose future directions for the development of novel disinfectant nanomaterials and the construction of advanced air purification devices.

MOF Embedded and Cu Doped CeO2 Nanostructures as Efficient Catalyst for Adipic Acid Production: Green Catalysis

Greatly efficient chemical processes are customarily based upon a catalyst activating the process pathway to achieve higher yields of a product with desired specifications. Catalysts capable of achieving good performance without compromising green credentials are a pre-requisite for the development of a sustainable process. In this study, CeO2 nanoparticles were tested for their catalytic activity with two different configurations, one as a hybrid of CeO2 nanoparticles with Zeolitic Immidazole Framework (ZIF-67) and second being doped Cu cations into CeO2 nanoparticles. Physicochemical and catalytic activity was investigated and compared for both systems. Each hybrid was synthesized by embedding the CeO2 nanoparticles into the microporous structure of ZIF-67, and Cu doped CeO2 nanoparticles were prepared by a facile hydrothermal route. As a catalytic test, it was employed for the oxidation of cyclohexene to adipic acid (AA) as an alternative to expensive noble metal-based catalysts. Heterogeneous ZIF-67/CeO2 found catalytical activity towards the oxidation of cyclohexene with nearly complete conversion of cyclohexene into AA under moderate and co-catalyst free reaction conditions, whereas Cu doped CeO2 nanoparticles have shown no catalytic activity towards cyclohexene conversion, depicting the advantages of the porous ZIF-67 structure and its synergistic effect with CeO2 nanoparticles. The large surface area catalyst could be a viable option for the green synthesis of many other chemicals.

Highly efficient Ru/CeO2 catalysts for formaldehyde oxidation at low temperature and the mechanistic study

Ru species have a high redox capacity on a CeO₂ support, and the metallic Ru species could be easily oxidized back to RuO_x species.

Hierarchical nanostructures self-assembled from δ-MnO2 ultrathin nanosheets and Mn3O4 octahedrons for efficient room-temperature HCHO oxidation

Self-assembling ultrathin active δ-MnO₂ nanosheets and Mn₃O₄ octahedrons into hierarchical texture enhances room-temperature formaldehyde oxidation at a low-level of Pt.

Fabrication of Pd/CeO2 nanocubes as highly efficient catalysts for degradation of formaldehyde at room temperature

The highly active Pd/CeO2 nanocube interface guarantees a high percentage of metallic Pd and the surface active O species is responsible for the complete decomposition of formaldehyde.

Abatement of formaldehyde with photocatalytic and catalytic oxidation: a review

Formaldehyde is one of the vital chemicals produced by industries, transports, and domestic products. Formaldehyde emissions adversely affect human health and it is well known for causing irritation and nasal tumors. The major aim of the modern indoor formaldehyde control study is in view of energy capacity, product selectivity, security, and durability for efficient removal of formaldehyde. The two important methods to control this harmful chemical in the indoor environments are photocatalytic oxidation and catalytic oxidation with noble metals and transition metal oxides. By harmonizing different traditional photocatalytic and catalytic oxidation technologies that have been evolved already, here we give a review of previously developed efforts to degrade indoor formaldehyde. The major concern in this article is based on getting the degradation of formaldehyde at ambient temperature. In this article, different aspects of these two methods with their merits and demerits are discussed. The possible effects of operating parameters like preparation methods, support, the effect of light intensity in photocatalytic oxidation, relative humidity, etc. have been discussed comprehensively.

Novel Materials for Combined Nitrogen Dioxide and Formaldehyde Pollution Control under Ambient Conditions

Formaldehyde (HCHO) and nitrogen dioxide (NO2) often co-exist in urban environments at levels that are hazardous to health. There is a demand for a solution to the problem of their combined removal. In this paper, we investigate catalysts, adsorbents and composites for their removal efficiency (RE) toward HCHO and NO2, in the context of creating a pollution control device (PCD). Proton-transfer-reaction mass spectrometry and cavity ring-down spectrometry are used to measure HCHO, and chemiluminescence and absorbance-based monitors for NO2. Commercially available and lab-synthesized materials are tested under relevant conditions. None of the commercial adsorbents are effective for HCHO removal, whereas two metal oxide-based catalysts are highly effective, with REs of 81 ± 4% and 82 ± 1%, an improvement on previous materials tested under similar conditions. The best performing material for combined removal is a novel composite consisting of a noble metal catalyst supported on a metal oxide, combined with a treated active carbon adsorbent. The composite is theorized to work synergistically to physisorb and oxidize HCHO and chemisorb NO2. It has an HCHO RE of 72 ± 2% and an NO2 RE of 96 ± 2%. This material has potential as the active component in PCDs used to reduce personal pollution exposure.

Bimetallic Catalysts for Volatile Organic Compound Oxidation

In recent years, the impending necessity to improve the quality of outdoor and indoor air has produced a constant increase of investigations in the methodologies to remove and/or to decrease the emission of volatile organic compounds (VOCs). Among the various strategies for VOC elimination, catalytic oxidation and recently photocatalytic oxidation are regarded as some of the most promising technologies for VOC total oxidation from urban and industrial waste streams. This work is focused on bimetallic supported catalysts, investigating systematically the progress and developments in the design of these materials. In particular, we highlight their advantages compared to those of their monometallic counterparts in terms of catalytic performance and physicochemical properties (catalytic stability and reusability). The formation of a synergistic effect between the two metals is the key feature of these particular catalysts. This review examines the state-of-the-art of a peculiar sector (the bimetallic systems) belonging to a wide area (i.e., the several catalysts used for VOC removal) with the aim to contribute to further increase the knowledge of the catalytic materials for VOC removal, stressing the promising potential applications of the bimetallic catalysts in the air purification.

Efficient activation of Pd/CeO2 catalyst by non-thermal plasma for complete oxidation of indoor formaldehyde at room temperature

Formaldehyde is a typical indoor air pollutant and its removal is essential to protect human health and meet environmental regulations. Efficient activation of Pd/CeO₂ catalyst by non-thermal plasma was investigated to achieve complete oxidation of formaldehyde at room temperature. The catalyst exhibited better activity and stability than conventional thermal reduced sample. Its HCHO conversion to CO₂ kept at over 80% during 300 min test at a gas hourly space velocity of 150, 000 mL/g/h and HCHO concentration of 100 ppm. While the conversion dropped from 70% to 50% within 300 min test for the sample reduced at 300 °C. Compared with thermal reduced catalyst, plasma reduced sample exhibited more abundant surface active oxygen species, smaller palladium particle size and narrower particle size distribution. Moreover, palladium particles were partial covered by ceria layer for thermal reduced sample. Although strong interaction between palladium and ceria could be formed, the loss of metallic palladium occurs and hence the oxygen activation and mobility abilities are blocked. In situ DRIFTs results suggested that the intermediates over Pd/CeO₂ catalyst were mainly formate, dioxymethylene and polyoxymethylene species, and the formate oxidation into CO₂ process was highly promoted in the presence of water.

The catalytic degradation of nitrobenzene by the Cu-Co-Fe-LDH through activated oxygen under ambient conditions

Efficient and low-cost catalysts for catalytic wet air oxidation (CWAO) under ambient conditions are of great significance for the degradation of hydrophobic organic contaminants. In this study, four LDH catalysts were prepared and their catalytic performance was studied by the degradation of nitrobenzene. The CuCoFe-LDH shows the best catalytic activity with an NB removal efficiency of 41.2%. The CuCoFe-LDH exhibited a typical layer structure, with a specific surface area of 167.32 m² g^-1, and Cu²⁺, Co²⁺ and Fe³⁺ were evenly dispersed on the crystal. The NB removal efficiency was increased by 12.5% through adding formic acid. After five recycling processes, the NB removal efficiency was 18.9% because 3.8 mg g^-1 of Co was leached out of the LDH. In the CWAO process, H₂O₂, ˙OH, ˙O₂^- and ¹O₂ were successfully formed through activated oxygen by the CuCoFe-LDH catalyst under ambient conditions. This work further broadens the application scope of layered double hydroxides (LDHs) in the degradation of organic pollutants by CWAO under ambient conditions.

Boosting the Removal of Diesel Soot Particles by the Optimal Exposed Crystal Facet of CeO2 in Au/CeO2 Catalysts

Optimized surface facet of the catalysts is an efficient strategy to boost catalytic purification of diesel soot as important components of atmospheric fine particles. Herein, we have elaborately constructed the nanocatalysts of Au nanoparticles supported on the well-defined CeO₂ (rod, cube, and polyhedron) with predominantly exposed facets of {110}, {100}, and {111}, respectively. The strong interaction between Au and CeO₂ with the optimal crystal facet is crucial to adjust the active site density for activated O₂, and the synergy effect of Au and the CeO₂{110} facet possesses the largest density of active sites compared with other crystal facets of {100} and {111}. The catalytic activity for soot combustion was tuned by exposed crystal facets of CeO₂. The Au/CeO₂-rod catalyst exhibits the highest catalytic activity (T₅₀ = 350 °C, TOF = 0.18 h^-1) and the lowest apparent activation energy (72 kJ mol^-1) during soot combustion. Based on the results of in situ Raman spectra, the formation and stability of oxygen vacancy located at the interface of the Au-O-Ce bond, boosting the key step of NO oxidation to NO₂, are dependent on the exposed crystal facets of CeO₂. It highlights a new strategy for the fabrication of high-efficient CeO₂-based catalysts for the removal of soot particles or other pollution.

Complete oxidation of formaldehyde over a Pd/CeO2 catalyst at room temperature: tunable active oxygen species content by non-thermal plasma activation

Formaldehyde is a main indoor pollutant and its removal is essential to protect human health and meet strict environmental regulations.

Supported ceria-modified silver catalysts with high activity and stability for toluene removal

Herein we fabricated the supported single-atom silver catalysts using an in situ molten salt method. The Mn₂O₃ nanowires supported single-atom silver catalyst (i.e., 0.06 wt% Ag/Mn₂O₃) exhibited excellent catalytic activity for toluene combustion, with the temperatures required for 50 and 90% of toluene conversions being 170 and 205 °C, respectively, at a space velocity of 40,000 mL/(g h). However, the toluene conversion at 205 °C quickly decreased from 90 to 30% within 2.5 h of on-stream reaction. Based on the various characterization results, we found that there were no aggregation of Ag particles, no change in crystal structure of the Mn₂O₃ nanowire support, and no carbon deposition on the catalyst surface, and the quick deactivation of 0.06 wt% Ag/Mn₂O₃ was mainly associated with the low oxygen activation ability. The proper CeO₂ addition to the 0.06 wt% Ag/Mn₂O₃ catalyst was found to not only improve the catalytic activity but also significantly enhance the stability of the catalyst. Toluene conversion at 195 °C over 0.63 wt% CeO₂-0.06 wt% Ag/Mn₂O₃ decreased by only 10% in 50 h of on-stream reaction. Because Ag and CeO₂ particles were highly dispersed on the Mn₂O₃ nanowire support, the oxygen species formed at the surface oxygen vacancies of CeO₂ could efficiently migrate to the active sites (i.e., the interface of Ag-Mn₂O₃) and replenish the surface reactive lattice oxygen species. Thus, the present single-atom silver catalyst is an alternative for commercial noble metal catalysts for the removal of VOCs.

Nanocatalysts for Electrocatalytic Oxidation of Ethanol

The use of ethanol as a fuel in direct alcohol fuel cells depends not only on its ease of production from renewable sources, but also on overcoming the challenges of storage and transportation. In an ethanol-based fuel cell, highly active electrocatalysts are required to break the C-C bond in ethanol for its complete oxidation at lower overpotentials, with the aim of increasing the cell performance, ethanol conversion rates, and fuel efficiency. In recent decades, the development of wet-chemistry methods has stimulated research into catalyst design, reactivity tailoring, and mechanistic investigations, and thus, created great opportunities to achieve efficient oxidation of ethanol. In this Minireview, the nanomaterials tested as electrocatalysts for the ethanol oxidation reaction in acid or alkaline environments are summarized. The focus is mainly on nanomaterials synthesized by using wet-chemistry methods, with particular attention on the relationship between the chemical and physical characteristics of the catalysts, for example, catalyst composition, morphology, structure, degree of alloying, presence of oxides or supports, and their activity for ethanol electro-oxidation. As potential alternatives to noble metals, non-noble-metal catalysts for ethanol oxidation are also briefly reviewed. Insights into further enhancing the catalytic performance through the design of efficient electrocatalysts are also provided.

Active Site-Directed Tandem Catalysis on Single Platinum Nanoparticles for Efficient and Stable Oxidation of Formaldehyde at Room Temperature

The application of tandem catalysis is rarely investigated in degrading organic pollutants in the environment. Herein, a tandem catalyst on single platinum (Pt) nanoparticles (Pt⁰ NPs) is prepared for the sequential degradation of formaldehyde (HCHO) to carbon dioxide gas [CO₂(g)] at room temperature. The synthesis approach includes coating of uniform Pt NPs on SrBi₂Ta₂O₉ platelets using a photoreduction process, followed by calcination of the sample in the atmosphere to tune partial transformation of Pt⁰ atoms to Pt²⁺ ions in the tandem catalyst. The conversion of HCHO to CO₂(g) is monitored by in situ Fourier transform infrared spectroscopy, which shows first conversion of HCHO to CO₃^2- ions onto Pt⁰ active sites and subsequently the conversion of CO₃^2- ions to CO₂(g) by neighboring Pt²⁺ species of the catalyst. The later process with Pt²⁺ species does not allow CO₃^2- poisoning of the catalyst. The enhanced activity of the prepared tandem catalyst to oxidize HCHO is maintained continuously for 680 min. Comparatively, the catalyst without Pt²⁺ shows activity for only 40 min. Additionally, the tandem catalyst presented herein performs better than the Pt/titanium dioxide (TiO₂) catalyst to degrade HCHO. Overall, the tandem catalyst may be applied to degrade organic pollutants efficiently.

Controllable synthesis of hierarchical nanoporous ε-MnO2 crystals for the highly effective oxidation removal of formaldehyde

Hierarchical nanoporous ε-MnO₂ crystals were prepared through thermal decomposition of hydrothermally-synthesized MnCO₃ precursors without any external templates or surfactants.

Selective oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid over Au/CeO2 catalysts: the morphology effect of CeO2

A morphological effect of Au/CeO₂ catalysts in 5-hydroxymethylfurfural (HMF) oxidation.

Au/Co promoted CeO2 catalysts for formaldehyde total oxidation at ambient temperature: role of oxygen vacancies

Cobalt enables formation of additional oxygen vacancies in Au/Co–CeO₂ and significantly boosts the ambient oxidation of formaldehyde.

Ultralow Pt Catalyst for Formaldehyde Removal: The Determinant Role of Support

Supported Pt catalyst has been intensively investigated for formaldehyde elimination owing to its superior reactivity at room temperature (RT). However, the high Pt content is challenging because of its high cost. Herein, we report PbO-supported Pt catalysts with only 0.1 wt % Pt, which can achieve complete conversion of formaldehyde and reliable stability at RT under demanding conditions. Both experiments and simulations demonstrate that PbO interacts strongly with the Pt species, resulting in tight Pb-O-Pt bonding at the metal/support interface and concomitant activation of the surface lattice oxygen of the support. Moreover, PbO exhibits an extremely high capacity of formaldehyde capture through methylene glycol chemisorption rather than the common hydroxyl-associated adsorption, presenting a different reaction mechanism because the active surface lattice oxygen in the vicinity of Pt species offers improved reactivity. This work provides a valuable example for the design of an efficient catalyst for formaldehyde and potentially oxidation of other carbohydrates.

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Pt% in catalyst for room temperature formaldehyde removal was reduced to 0.1 wt %

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100% formaldehyde removal and reliable stability was achieved at room temperature

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PbO interacts strongly with the Pt species to form tight Pb-O-Pt bonding

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The active surface lattice oxygen close to Pt species offers improved reactivity

Heterogeneous gap-mode nanostructure for surface-enhanced Raman spectroscopic evaluation of charge transfer between noble metal nanoparticles and formaldehyde vapor

Gap-mode nanostructures offer a reliable, scalable and controllable Raman substrate with high signal enhancement, and they are widely used in surface-enhanced Raman spectroscopy. Heterogeneous gap-mode structures composed of different types of nanoparticles with the underlying substrate have been studied only in terms of understanding the electromagnetic field enhancement mechanism up to now, just by focusing on the role of hot spot as enhancing the Raman signal itself. In this study, gold and platinum nanoparticle-based heterogeneous gap-mode structures were fabricated on gold surface, and used to evaluate minute changes in the surface charged state (surface potential) of the nanoparticle interacting with different organic vapors. By monitoring the surface-enhanced Raman signal change of isonitrile probes in the hot spot, it was revealed that gold and platinum nanoparticles show opposite directions of charge transfer over the same formaldehyde treatment. This strategy offers a new way to evaluate the charge transfer phenomenon between organic vapor and nanoparticles, which is especially important in catalytic application, using conventional surface-enhanced Raman spectroscopy.

A Novel Redox Precipitation to Synthesize Au-Doped α-MnO2 with High Dispersion toward Low-Temperature Oxidation of Formaldehyde

A novel method of redox precipitation was applied for the first time to synthesize a Au-doped α-MnO₂ catalyst with high dispersion of the Au species. Au nanoparticles (NPs) can be downsized into approximate single atoms by this method, thereby realizing highly efficient utilization of Au element as well as satisfying low-temperature oxidation of formaldehyde (HCHO). Under catalysis of the optimal 0.25% Au/α-MnO₂ catalyst, a polluted stream containing 500 ppm HCHO can be completely cleaned at 75 °C with the condition of a weight hourly space velocity (WHSV) of 60000 mL/(g h). Meanwhile, the catalyst retains good activity for removal of low-concentration HCHO (about 1 ppm) at ambient temperature with a high WHSV, and exhibits a high tolerance to water and long-term stability. Our characterization of Au/α-MnO₂ and catalytic performance tests clearly demonstrate that the proper amount of Au doping facilitates formation of surface vacancy oxygen, lattice oxygen, and charged Au species as an active site, which are all beneficial to catalytic oxidation of HCHO. The oxidation of HCHO over Au-doped α-MnO₂ catalyst obeys the Mars-van Krevelen mechanism as evidenced by in situ diffuse reflectance infrared Fourier transform spectroscopy.

Fabrication of ultralong ceria nanobelts via a coordination polymer precursor method

Ultralong cerium-based coordination polymer (CP) nanobelts have been successfully synthesized through a facile solvothemal approach. After calcination in air and being loaded 1 wt% Pt, the catalyst showed satisfactory activity of catalytic reduction of p-nitrophenol.

Potassium associated manganese vacancy in birnessite-type manganese dioxide for airborne formaldehyde oxidation

The relationship between K⁺ and Mn vacancies and the significant effect of the K⁺ content on the structure, morphology and catalytic activity of birnessite-type MnO₂ for HCHO oxidation was systematically studied.