Activity For Oxidation Research Articles

SILP Type Catalyst Based on H3PMo12O40: Composition of Heteropolyanions According to Mass Spectrometry Data and Activity in Oxidation of Sulfur-Containing Substrates

SILP Type Catalyst Based on H3PMo12O40: Composition of Heteropolyanions According to Mass Spectrometry Data and Activity in Oxidation of Sulfur-Containing Substrates

Revealing Dynamics and Competitive Mechanism of Gas-Induced Surface Segregation of PdFe0.08 Dilute Alloy by Multi-Dimensional Imaging.

The restructuring of dilute alloys under gas environments has shown a great impact on their catalytic performance due to intriguing structural sensitivity, but the structural dynamics and underlying mechanism remains elusive. Herein, we directly resolved the distinct dynamic behaviors of PdFe0.08 dilute alloys under CO or O2 environment by multidimensional imaging. The stronger binding of gaseous CO with Fe atoms stimulates Fe segregation out of the PdFe0.08, resulting in 3D growth of Fe islands, whereas the dissociative adsorption of O2 results in 2D layer-by-layer growth of segregated FeO as encapsulation overlayers that bind strongly with the Pd surface underneath. Such varied structures remarkably tune the catalytic activity for CO oxidation, showing a considerably high activity for a CO-treated sample. Our results reveal the competitive mechanism between adsorbate-metal and metal-metal interaction for gas-induced surface segregation, which should be highly considered for the rational design of dilute alloys with dynamically tuned structure and reactivity.

Enrichment and catalysis effect of 2D/2D g-C3N4/Ti3C2 for promoting organic matter degradation and heavy metal reduction in plasma systems: Unveiling the promotion and redox mechanism.

This work proposes a novel plasma-assisted 2D/2D g-C3N4/Ti3C2 system for treatment of organics-heavy metals composite wastewater. Unlike traditional materials in plasma system, 2D/2D g-C3N4/Ti3C2 not only improved the mass transfer efficiency of plasma by gathering both reactive species and pollutants onto the surface, but also induced photocatalytic reactions. Besides, the higher specific surface area and faster carrier separation rate can enhance the oxidation and reduction activity, and then promoted organic matter degradation and heavy metal reduction. Remarkably, the removal efficiency of sulfamethoxazole (SMX) and Cr(VI) increased by 16.5% and 73.1% respectively when introducing 2D/2D g-C3N4/Ti3C2. Roles of·OH,·H,·O2-, 1O2, e-, and h+ in SMX oxidation and Cr(VI) reduction are clarified. The primary aggregated·OH and 1O2 dominate the degradation of SMX. The influencing factors, synergistic mechanism between plasma and catalyst, and redox mechanism were clarified. This work provides a breakthrough idea for treatment of organics-heavy metals composite wastewater.

High‐Throughput Screening of Dual‐Atom Catalysts for Methane Combustion: A Combined Density Functional Theory and Machine‐Learning Study

AbstractCeria‐supported precious metal catalysts have undergone extensive investigation for the catalytic methane combustion. However, it remains a significant challenge to achieve both highly synergistic oxidation activity and efficient atom utilization remains a challenge for commonly used supported nanoparticles and single‐atom catalysts. Dual‐atom catalysts (DACs) emerges as a frontier of advanced catalysts, presenting unique catalytic properties that benefit from the synergy of neighboring metal sites. In this study, 361 ceria‐supported DACs (M1M2/CeO2) encompassing combinations of 19 transition metals are systematically explored. Using high‐throughput density functional theory calculations, the structures, stability as well as activity of M1M2/CeO2 are assessed. Notably, Au1Ga1/CeO2 is identified as a promising DAC exhibiting high activity for methane total oxidation, substantiated by comprehensive DFT‐calculated reaction pathways. Furthermore, employing six machine‐learning algorithms, the structure‐properties relationship is explored within ceria‐based DACs and highlight the importance of oxidation states and atomic radii of doped metals as the descriptors. The trained model by computational dataset exhibits high accuracy and predict a more active Mn1Au1/CeO2 than those screened using only DFT datasets. The high‐throughput strategy demonstrated in this work not only provides insights into the rational design of methane oxidation catalysts, but also paves the way for exploring DACs for diverse applications.

Influence of pharmacotherapy on function of biotransformation of xenobiotics liver in patients with neuropsychiatric disorders

BACKGROUND: The mechanisms of drug interactions of psychotropic drugs are associated with the processes of drug biotransformation by enzymes of microsomal oxidation of cytochrome P-450 in the liver. Various drugs can increase or decrease the activity of enzymes of the cytochrome P450-dependent system. AIM: To evaluate the effect of pharmacotherapy with psychotropic drugs: alprazolam, bromazepam, lithium carbonate on the metabolic rate of the model substrate antipyrine in saliva in patients with neuropsychiatric disorders; the effect of the enzyme-inducing activity of the original anticonvulsant 1-[(3-chlorophenyl)(phenyl)methyl]urea on the pharmacokinetic parameters of antipyrine in healthy volunteers. MATERIALS AND METHODS: 34 male patients were divided into three groups according to the nosological forms of diseases according to ICD-10: Group 1 — heading F43.23 and F43.25; 2 — F06.61; 3 — F41.2. Patients in the group 1 were prescribed alprazolam, in the 2 — bromazepam, in the 3 — lithium carbonate, for a course of 21 days. The comparison group consisted of 10 healthy volunteers. The original anticonvulsant was prescribed to the volunteers. Determination of the pharmacokinetics of antipyrine parameters as a test witness of the processes of elimination from the body was carried out in saliva before and after the end of therapy at a dose of 10 mg/kg once. RESULTS: Alprazolam administration by patients of group 1 at a dose of 0.5–1.5 mg/day for 21 days did not significantly affect the pharmacokinetic parameters of antipyrine: T1/2, Clt, AUC. Alprazolam did not change the elimination of antipyrine from the saliva of patients. In patients of the group2, who received bromazepam at a dose of 6–12 mg / day,a background decrease in T1/2, an increase in Clt, a decrease in AUC due to concomitant therapy were noted. Comparison of the pharmacokinetic parameters of antipyrine under the influence of bromazepam with background values not reveal significant differences. Therapy with lithium carbonate at a dose of 500–1000 mg/day in patients of the group 3 did not change the parameters of antipyrine elimination. The obtained data indicate that the drugs do not affect the activity of liver microsomal oxidation in patients. The study of the effect of 1-[(3-chlorophenyl)(phenyl)methyl]urea on the pharmacokinetic parameters of antipyrine in volunteers revealed a diametrically opposite result: a significant decrease in T1/2 by 2 times, an increase in Clt and a decrease in AUC, which indicates accelerated elimination of antipyrine from the saliva of the subjects and indicates the induction of liver microsomal oxidation. CONCLUSIONS: Pharmacotherapy using the studied psychotropic drugs in patients is not associated with the induction or inhibition of liver enzymes, which indicates the absence of drug pharmacokinetic interference. The original anticonvulsant 1-[(3-chlorophenyl)(phenyl)methyl]urea stimulated the induction of liver microsomal oxidation in volunteers.

How Ir‐Rh Alloys Improve Electrochemical Ammonia Oxidation Activity Studied by Density Functional Theory

The electrochemical ammonia oxidation reaction (AOR) has applications in hydrogen storage and ammonia waste remediation. Using density functional theory, we investigate the mechanism of AOR on Ir, Rh, and their alloys at varied atomic ratios (Ir75Rh25, Ir50Rh50, and Ir25Rh75) towards N2(g), NO2–(aq), and NO3–(aq) formation. This work introduces a method for computational alloy design by considering both electronic energy and configurational entropy. The structures considered are selective to N2(g) formation and all favoured *N‐N coupling. An Ir50Rh50 alloy was found to reduce the theoretical onset potential for N2(g) formation relative to pure Ir while not exhibiting a downhill coupling step corresponding to catalyst poisoning by *N as shown for pure Rh, consistent with previous experimental work. The formation of NO2–(aq) and NO3–(aq) demand significantly higher potentials, typically limited by the final hydroxylation step before desorption.

Manipulating the H2O2 Reactivity on Pristine Anatase TiO2 with Various Surface Features and Implications in Oxidation Reactions.

Anatase TiO2 is commonly used as a catalyst/support in reactions involving H2O2, yet the understanding of interactions between common TiO2 surfaces and H2O2 remains limited. Herein, we synthesized well-defined TiO2 crystallites with (101), (001), and fluorine-modified (001) [F-(001)] surfaces to examine how surface features, including the arrangement of five-coordinated Ti (Ti5c) sites and the presence of fluorine, influence H2O2 activation. Our findings reveal that these surface features significantly affect the physiochemical properties of adsorbed H2O2. Specifically, fluorine on the F-(001) surface introduces an additional hydrogen bond to the Ti5c-peroxo species, altering the electronic structure of H2O2 compared to those with the (101) and (001) surfaces. Using cyclohexene as a probe substrate, we successfully distinguished the reactivities of the Ti5c-peroxo species. The activity of those on the F-(001) surface was significantly higher than the activity of those on the (001) surface, while the (101) surface showed negligible oxidation activity. These insights can guide the design of TiO2-based catalysts for H2O2-related reactions.

A General Approach for Metal Nanoparticle Encapsulation Within Porous Oxides.

Encapsulation of metal nanoparticles within oxide materials has been shown as an effective strategy to improve activity, selectivity, and stability in several catalytic applications. Several approaches have been proposed to encapsulate nanoparticles, such as forming core-shell structures, growing ordered structures (zeolites or metal-organic frameworks) on nanoparticles, or directly depositing support materials on nanoparticles. Here, a general nanocasting method is demonstrated that can produce diverse encapsulated metal@oxide structures with different compositions (Pt, Pd, Rh) and multiple types of oxides (Al2O3, Al2O3-CeO2, ZrO2, ZnZrOx, In2O3, Mn2O3, TiO2) while controlling the size and dispersion of nanoparticles and the porous structure of the oxide. Metal@polymer structures are first prepared, and then the oxide precursor is infiltrated into such structures and the resulting material is calcined to form the metal@oxide structures. Most Pt@oxides catalysts show similar catalytic activity, demonstrating the availability of surface Pt sites in the encapsulated structures. However, the Pt@Mn2O3 sample showed much higher CO oxidation activity, while also being stable under aging conditions. This work demonstrated a robust nanocasting method to synthesize metal@oxide structures, which can be utilized in catalysis to finely tune metal-oxide interfaces.

Microwave assisted synthesis of ErxYbyCa1-x-yMoO4 nano-phosphor for efficient temperature sensing and catalytic applications

Here, Er/Yb Co-doped CaMoO4 materials (ErxYbyCa1−x−yMoO4 NPs where x = 0, 0.01 and y = 0, 0.05, 0.10, 0.15, 0.20) were prepared by microwave-assisted method and its pure-tetragonal structure were confirmed by X-ray diffraction spectra (XRD), Rietveld-refinement and Raman-vibrational spectra. The transmission-electron microscopy (TEM) study indicates the formation of nearly spherical shaped nanomaterial with average size of ~ 15 nm. Additionally, absorption and emission properties were studied by UV–Visible–NIR and photoluminescence (PL) spectrometer. The UV–Visible–NIR spectra attribute absorption of Er3+ ion in visible region (380–700 nm) and absorption of Yb3+ ion in near-infrared region (700–1400 nm). Moreover, PL up-conversion spectra of the sample recorded under excitation wavelength 980 nm. The PL peaks were observed at 530, 544–552, and 656–670 nm. Prominent PL-intensity was observed for Er0.01Yb0.15Ca0.84MoO4 phosphor. Temperature dependent PL study reveals that present phosphor is robust phosphor for temperature sensor. In addition, Er3+/Yb3+ doped CaMoO4 nanomaterials exhibited excellent activity and selectivity in the aerial oxidation of benzoin over benzyl under oxidant-free reaction conditions. The synergistic effect Er3+/Yb3+ co-doing in CaMoO4 matrix was observed, where only CaMoO4 material found to be inactive towards above oxidation reaction. Moreover, the oxidation of primary benzyl-alcohols was furnished in presence of tertiary butyl hydroperoxideas oxidant.

Asymmetric coordinative modulation boosting the activity and thermal stability of Pt1/CeO2 for CO oxidation under harsh condition

Supported metal catalysts play a central role in chemical industry, but it remains a formidable challenge to realize high activity while maintaining atomically dispersed status to maximize atom efficiency under harsh conditions. Herein, a novel strategy of constructing asymmetric coordination Pt active sites via coating N-doped carbon onto ceria supported Pt single atoms (Pt1/CeO2@CN) is proposed, through which superior low-temperature CO oxidation activity and satisfactory thermal stability are achieved simultaneously. Experimental and density functional theory results confirm that the unique asymmetric N2-Pt1-O2 coordinative configuration on Pt1/CeO2@CN tailors the electronic properties of Pt 5d states, increasing the turnover frequency by 15 times for CO oxidation at 120 °C compared with that on Pt1/CeO2 and sustaining the atomically dispersed status of Pt at as high as 400 °C under H2-containing atmosphere. This strategy suggests a promising avenue to fabricating highly active and stable supported metal catalysts for practical applications under harsh conditions.

Synergistic effect of FeOOH cocatalyst and Al2O3 passivation layer on BiVO4 photoanode for enhanced photoelectrochemical water oxidation

BiVO4 is one of the most attractive photoanodes for water oxidation due to its 2.4 eV narrow band gap, suitable band edge position, good stability in aqueous solution, low cost and non-toxicity. However, due to some inherent disadvantages such as low carrier mobility, severe charge recombination and slow water oxidation kinetics, the actual BiVO4 photocurrent density is often lower than the theoretical value of 7.5 mA cm−2. In this paper, BiVO4 was modified by alkali-treated Al2O3 passivation layer and FeOOH, and the photocurrent density of BiVO4 reached an astonishing 3.8 mA cm−2 at 1.23 VRHE, and the ABPE (applied bias photon-to-current efficiency) was close to 1 %. The detailed structural characterization and electrochemical test show that Al2O3 prepared by ALD (atomic layer deposition) can play a role in passivation of BiVO4 surface state after alkali treatment, inhibit electron hole recombination on BiVO4 surface, and accelerate hole transfer. As a hole storage layer and catalyst layer, FeOOH promoted the interfacial hole transfer, increased the active sites at the electrode electrolyte interface, and significantly increased the water oxidation activity. This work provides a novel method to enhance the performance of water electrolysis by using ALD to assist passivation of bismuth vanadate photoanode surface states.

Role of methanotrophic communities in atmospheric methane oxidation in paddy soils

Wetland systems are known methane (CH4) sources. However, flooded rice fields are periodically drained. The paddy soils can absorb atmospheric CH4 during the dry seasons due to high-affinity methane-oxidizing bacteria (methanotroph). Atmospheric CH4 uptake can be induced during the low-affinity oxidation of high-concentration CH4 in paddy soils. Multiple interacting factors control atmospheric CH4 uptake in soil ecosystems. Broader biogeographical data are required to refine our understanding of the biotic and abiotic factors related to atmospheric CH4 uptake in paddy soils. Thus, here, we aimed to assess the high-affinity CH4 oxidation activity and explored the community composition of active atmospheric methanotrophs in nine geographically distinct Chinese paddy soils. Our findings demonstrated that high-affinity oxidation of 1.86 parts per million by volume (ppmv) CH4 was quickly induced after 10,000 ppmv high-concentration CH4 consumption by conventional methanotrophs. The ratios of 16S rRNA to rRNA genes (rDNA) for type II methanotrophs were higher than those for type I methanotrophs in all acid-neutral soils (excluding the alkaline soil) with high-affinity CH4 oxidation activity. Both the 16S rRNA:rDNA ratios of type II methanotrophs and the abundance of 13C-labeled type II methanotrophs positively correlated with high-affinity CH4 oxidation activity. Soil abiotic factors can regulate methanotrophic community composition and atmospheric CH4 uptake in paddy soils. High-affinity methane oxidation activity, as well as the abundance of type II methanotroph, negatively correlated with soil pH, while they positively correlated with soil nutrient availability (soil organic carbon, total nitrogen, and ammonium-nitrogen). Our results indicate the importance of type II methanotrophs and abiotic factors in atmospheric CH4 uptake in paddy soils. Our findings offer a broader biogeographical perspective on atmospheric CH4 uptake in paddy soils. This provides evidence that periodically drained paddy fields can serve as the dry-season CH4 sink. This study is anticipated to help in determining and devising greenhouse gas mitigation strategies through effective farm management in paddy fields.

Photothermally Reinforced Nanozyme Remodeling Tumor Microenvironment of Redox and Metabolic Homeostasis to Enhance Ferroptosis in Tumor Therapy.

The acidity and high GSH level in the tumor microenvironment (TME) greatly limit the antitumor activity of nanozymes. Thus, enhancing nanozymes' activity is fundamentally challenging in tumor therapy. Although the combination of photothermal therapy (PTT) and nanozymes can enhance the catalytic activity, cancer cells will overexpress heat shock proteins (HSPs) at high temperature, aggravating the heat resistance of tumor cells, which in turn compromises the outcome of chemodynamic therapy. Herein, we propose an iron-doped metal-organic framework nanozyme (IB@Fe-ZIF8@PDFA) that can be activated under the weak acidity and high level of GSH, demonstrating the activities of GSH oxidation (GSH-OXD), peroxidase (POD), and NADH oxidase (NADH-OXD). Under laser irradiation, it displays photothermal-enhanced multienzyme activities to simultaneously eliminate tumors and inhibit tumor metastasis. While consuming endogenous GSH, IB@Fe-ZIF8@PDFA promotes the decomposition of H2O2 into ·OH, enhancing ferroptosis in tumor cells. Surprisingly, IB@Fe-ZIF8@PDFA nanozyme can oxide NADH and subsequently limit the ATP supply, reducing the expression of HSPs and significantly weakening the heat resistance of tumor cells during PTT. Meanwhile, H2O2 is generated during this procedure, which can endogenously replenish the consumed H2O2. Thus, this IB@Fe-ZIF8@PDFA nanozyme constitutes a self-cascading platform to consume GSH and NADH, endogenously replenish the H2O2 and continuously generate ·OH to facilitate ferroptosis by disrupting the redox and metabolic homeostasis in tumor cells, achieving tumor elimination and tumor metastasis inhibition.

Co single atoms/nanoparticles over carbon nanotubes for synergistic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid

The preparation of high-value 2,5-furandicarboxylic acid (FDCA) from biomass-based platform compound 5-hydroxymethylfurfural (HMF) is an important synthetic reaction, as the resulting FDCA holds promise to replace terephthalic acid to produce environmentally friendly polyester materials. However, due to the complex tandem nature of the oxidation of HMF to FDCA, which involves several stable intermediates, efficient conversion of HMF and achieving a high FDCA yield remain challenging. Herein, a catalyst of Co SAs/NPs@N-CNTs comprising Co single atoms (Co SAs) alongside Co nanoparticles (Co NPs) supported on carbon nanotubes (CNTs) was synthesized. Co SAs/NPs@N-CNTs exhibited outstanding catalytic activity for the selective oxidation of HMF to FDCA, achieving 100% HMF conversion and 94.2% FDCA yield. This remarkable performance was attributed to the synergistic effect between Co SAs and Co NPs. Poisoning and acid treatment experiments indicated that Co SAs served as the active sites, while Co NPs did not directly act as active sites. Instead, Co NPs merely assisted the Co SAs on the sidelines, facilitating the efficient conversion of HMF into various intermediates and promoting the further conversion of these intermediates into FDCA, thereby achieving high FDCA productivity. This strategy offers new insights for designing efficient catalysts for complex tandem reactions.

Exploring Pt-Cu synergistic effects on porous SiO2 support with different Pt loadings for low-temperature oxidation of CO and C3H6

To address the high cost of noble metals, this study aims to optimize Pt loading and the synergistic effect of Cu on porous SiO2 support for low-temperature oxidation of CO and C3H6. A simulated test bench system was used to evaluate the performance of PtxCu1/SiO2 (where x= 0.3, 0.5, 0.7, and 1 wt%), Cu1/SiO2 and Ptx/SiO2 (where x= 0.5 and 1 wt%) catalysts with varying Pt loadings. Comprehensive characterization, including BET, XRD, SEM, TEM, and XPS was conducted to assess particle size, structure, and surface morphology. The effects of Pt incorporation on reduction and oxidation properties were further examined using H2-TPR and CO-TPD techniques. Results demonstrated a significant enhancement in catalytic activity with the addition of Cu confirming a synergistic interaction between Pt and Cu. This synergy was particularly pronounced in lower Pt loadings, where PtxCu1/SiO2 composites outperformed Ptx/SiO2 in catalytic activity. Pt addition reduced the particle size, which resulted in the creation of PtCu alloy, with 1 and 0.7 % wt Pt loading exhibiting comparable effects in CO conversion and 0.7 % Pt loading exhibiting better activity at higher temperatures in C3H6 oxidation indicating that catalytic activity was maintained even with a reduced Pt loading. Additionally, minimal difference in activity for C3H6 oxidation was observed among PtxCu1/SiO2 catalysts with 0.7, 0.5, and 0.3 wt% Pt loadings as indicated by T50 and T80 values. Reducing Pt loading from 0.7 wt% had minimal impact on catalytic efficiency for C3H6 oxidation with catalysts maintaining high activity. 0.7 wt% Pt loadings provide sufficient active sites for effective CO and HC oxidation. The enhanced catalytic activity and stability of bimetallic catalysts over monometallic Cu/SiO2 and Pt/SiO2 result from the simultaneous presence of active sites created by the synergetic effect of PtCu alloy formation with optimal ratio and well-optimized surface. These findings demonstrate the potential to optimize Pt usage without compromising catalytic performance, offering a cost-effective approach to catalyst design.

The key role of the second material's OER activity on MOR durability enhancement of the Pt alloys

Pt-based precious metal catalysts are generally regarded as the best catalyst materials for direct methanol fuel cells due to their high inherent methanol oxidation (MOR) activity. However, the commercial application of Pt catalyst is still facing with severe durability problem. The CO formed by the incomplete oxidation of methanol will occupy the Pt active site, hindering the further progress of the MOR reaction and causing the rapid attenuation of the activity. In this work, a MOR durability enhancement strategy that relation to the OER performance of the second materials M (M=Ni, Co, Fe and Cu) is reported. The precise electrochemical test results showed that the MOR durability of Pt-M alloy changes with the second material, which is related to the OER activity of M materials. The smaller the overpotential and tafel slopes of the M material, the better the MOR durability. Via M material screening, the Co element with the lowest OER overpotential among M promoted the Pt-Co alloy material with the highest MOR durability, resulting an excellent durability sustain 7000 times CV cycles with just 0.53 A mg−1Pt mass activity loss. According to the current generally accepted OER and MOR reaction mechanism, the association of MOR durability with OER activity is most likely derived from the same reaction step of M-OH formation, which played a key role on both reaction. This relationship between OER overpotential and MOR durability helps to screen the second material from the perspective of OER activity to improve the MOR durability of Pt catalysts, which is of great significance for the development of Pt-based CO-resistant MOR catalysts.

Elucidating the intrinsic relationship between redox properties of CeO2 and CH4 oxidation activity: A theoretical perspective.

Methane (CH4) oxidation is an important reaction to reduce the greenhouse effect caused by incomplete combustion of CH4. Here, we explored the mechanism of CH4 oxidation catalyzed by CeO2 and Ni-doped CeO2, focusing on the redox properties of these catalyst surfaces, using density functional theory (DFT). We found that the barriers for CH4* activation and H2O* formation are correlated with the surface redox capacity, which is enhanced by Ni doping. Furthermore, the complete reaction mechanism is explored by DFT calculations and microkinetic simulations on bare and Ni-doped CeO2 surfaces. Our calculations suggest that the doping of Ni leads to a much higher overall reactivity, due to a balance between the CH4* activation and H2O* formation steps. These results provide insights into the CH4 oxidation mechanism and the intrinsic relationship between redox properties and the activity of CeO2 surfaces.

Revealing the differences in CO oxidation activity of Fe-CeO2, Fe2O3, and CeO2 using operando CO2-DRIFTS-MS: Carbonate species and desorption process

The carbonate on the catalyst surface is the key factor limiting carbon monoxide (CO) oxidation activity. However, the relationship between different carbonate species and surface oxygen species is not clear. In this paper, Fe-CeO2, Fe2O3, and CeO2 catalysts prepared by aerosol method are selected as the research target, and operando DRIFTS-MS is used as the main characterization method. Fe-CeO2 has good redox properties resulting in the best CO oxidation activity (350°C) and CO2 selectivity (98 %). Operando DRIFTS-MS results indicate that surface M=O species play a crucial role in the catalyst's activity, demonstrating the ability to react with CO at low temperatures. Notably, a high concentration of M=O facilitates the formation of monodentate carbonate (vas(CO32−)) (vas(CO32−) decomposes at 100°C). With increasing temperature, CeO and M-O-Ce also react with CO and produce M-Ov-Ce (oxygen vacancy). CO adsorption on M2+-O22− or M sites to form vas(OCO) or vs(OCO). The decomposition temperature of vs(OCO) exceeds that of vas(CO32−) significantly, and its presence serves as the crucial step in the oxidation of CO. The above conclusions reveal the relationship between surface carbonate and oxygen, and provide a theoretical basis for regulating the surface structure of catalysts.

Effect of flame temperature on structure and CO oxidation properties of Pt/CeO2 catalyst by flame-assisted spray pyrolysis

Flame synthesis offers the potential for the synthesis of structure-controlled catalysts. In this study, Pt/CeO2 nanoparticles were synthesized via flame-assisted spray pyrolysis (FASP) and used as CO oxidation catalysts. The catalysts were synthesized using a burner diffusion flame at three different flame temperatures (maximum flame temperatures, Tf = 1556, 1785, and 2026 K), and their particle structure and CO oxidation activity were evaluated. The synthesized Pt/CeO2 catalysts had a bimodal structure containing 100 nm-scale CeO2 loaded with 10 nm-scale Pt and fine CeO2 less than 10 nm loaded with highly dispersed Pt (less than 1 nm). As the flame temperature increases from 1556 to 2026 K, the formation of fine CeO2 particles dominates, resulting in an increase in BET specific surface area from 7.97 to 112 m2/g and Pt dispersion from 4.67 to 20.6%. Insight into the particle formation routes that determine the catalyst structure is provided by numerical simulation of droplet evaporation in a burner flame. CO oxidation experiments showed that the temperature at which CO conversion reached 100% (T100) decreased from 513 to 378 K with increasing flame temperature in FASP. In addition, the thermal stability test showed that the Pt dispersion after thermal degradation was higher for Pt/CeO2 catalyst made by FASP at Tf = 2026 K than that prepared by the impregnation method, and the T100 for CO oxidation was lower by 20 K.

Electrochemical synthesized copper mesh catalysts for catalytic combustion: A comprehensive study of Mn doping and atmospheric conditions during calcination

Metal-based monolithic catalysts offer significant advantages in heterogeneous catalysis attributed to their exceptional thermal conductivity and mechanical strength. However, controlling the loading of active components on metallic substrates remains a major challenge. Here, we synthesized a Mn-doped Cu mesh catalyst using a facile electrochemical method, allowing the active components to grow directly on Cu mesh without extra pretreatments or binding agents. The synthesized catalyst exhibits approximately a 30 % increase in carbon monoxide oxidation activity at 100°C and a 60 % increase in toluene oxidation activity at 240°C compared to the Mn-free Cu mesh catalyst. We found that calcination in inert gases enhances interactions between Cu and Mn species, leading to more oxygen vacancies and adsorption sites for reactants. This investigation paves the way for fabricating multi-metal monolithic catalysts on metallic substrates.