Enhanced Redox Properties Research Articles

Manipulation of Mn/Ce ratio for deep chlorobenzene oxidation: Catalytic mechanisms and byproducts analysis

In this research, a sequence of spatial porous MnCeOx catalysts with varying Mn/Ce from 3:1 to 1:7 were synthesized using the sol–gel method for chlorobenzene (CB) oxidation. Mn1Ce1 exhibited the best performance due to its high lattice oxygen content and the strong interaction between Ce and Mn. The increase in Mn content in CeO2 catalysts resulted in enhanced redox properties and acidity, which was beneficial for the adsorption and activation of CB, thus enhancing the selectivity and the desorption of HCl on the catalyst surface. Carbon deposition and the formation of metal chloride were the main reasons for catalyst deactivation. At low temperature regions (150 ∼ 300 °C), insufficient oxidation capability and the chlorine deposition on the catalyst surface resulted in the formation of various chlorinated compounds. As the temperature increases (300 ∼ 450 °C), the release of HCl and more reactive oxygen species is available on the catalytic interface, generating various oxygen-containing degradation intermediates. This work proposed a fine-designed, low-cost mixed metal oxide catalysts for low temperature CB oxidation, and provided novel in-depth understandings of degradation intermediate formation thermodynamics. Our findings would be helpful for deep purification of chlorinated VOCs polluted industrial tail gas.

Anionic ring-opening polymerization of ferrocenylcyclosiloxanes: a comprehensive structural study

In this study, a comprehensive structural analysis of the linear redox-active ferrocenyl-containing polysiloxanes (FPSs) was performed by the liquid-state 1H, 13C, and 29Si nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography (GPC), and cyclic voltammetry. FPSs with tunable Fc unit content ranging from 20 to 100 mol% were obtained by anionic ring-opening polymerization (AROP). The 29Si NMR spectroscopy indicates the successful anionic homopolymerization of the mono- and tetraferrocenyl-substituted cyclotetrasiloxanes (Fc4D4 and Fc1D4) by appearance of new signals of Si atoms corresponding to a polymer backbone. An analysis of pentad assignments in 29Si NMR determined the anionic copolymerization of Fc4D4 with D4 by indicating signals of neighboring Si atoms from different types of polymer units (DF and D), which differ from the signals of homopolymers. The Mayo-Lewis copolymerization constants of Fc4D4 and D4 were determined by the Fineman–Ross method. The molecular masses and unimodal molecular weight distribution of FPSs were estimated by using GPC. FPSs possess redox-activity. Thus, the proposed comprehensive approach analyzes structural features of the functional silicones with enhanced redox properties, which can be applied in (opto)electronics, coatings, and biomedicine.

Mechanistic insights into the conversion of flavin adenine dinucleotide (FAD) to 8-formyl FAD in formate oxidase: a combined experimental and in-silico study

Formate oxidase (FOx), which contains 8-formyl flavin adenine dinucleotide (FAD), exhibits a distinct advantage in utilizing ambient oxygen molecules for the oxidation of formic acid compared to other glucose-methanol-choline (GMC) oxidoreductase enzymes that contain only the standard FAD cofactor. The FOx-mediated conversion of FAD to 8-formyl FAD results in an approximate 10-fold increase in formate oxidase activity. However, the mechanistic details underlying the autocatalytic formation of 8-formyl FAD are still not well understood, which impedes further utilization of FOx. In this study, we employ molecular dynamics simulation, QM/MM umbrella sampling simulation, enzyme activity assay, site-directed mutagenesis, and spectroscopic analysis to elucidate the oxidation mechanism of FAD to 8-formyl FAD. Our results reveal that a catalytic water molecule, rather than any catalytic amino acids, serves as a general base to deprotonate the C8 methyl group on FAD, thus facilitating the formation of a quinone-methide tautomer intermediate. An oxygen molecule subsequently oxidizes this intermediate, resulting in a C8 methyl hydroperoxide anion that is protonated and dissociated to form OHC-RP and OH−. During the oxidation of FAD to 8-formyl FAD, the energy barrier for the rate-limiting step is calculated to be 22.8 kcal/mol, which corresponds to the required 14-hour transformation time observed experimentally. Further, the elucidated oxidation mechanism reveals that the autocatalytic formation of 8-formyl FAD depends on the proximal arginine and serine residues, R87 and S94, respectively. Enzymatic activity assay validates that the mutation of R87 to lysine reduces the kcat value to 75% of the wild-type, while the mutation to histidine results in a complete loss of activity. Similarly, the mutant S94I also leads to the deactivation of enzyme. This dependency arises because the nucleophilic OH− group and the quinone-methide tautomer intermediate are stabilized through the noncovalent interaction provided by R87 and S94. These findings not only explain the mechanistic details of each reaction step but also clarify the functional role of R87 and S94 during the oxidative maturation of 8-formyl FAD, thereby providing crucial theoretical support for the development of novel flavoenzymes with enhanced redox properties.

Co doping induced phase transition and its distinct effects on the catalytic performance of MnO2 toward toluene oxidation

Manganese oxides are very important and conventional catalysts that have demonstrated appreciable catalytic activity for the oxidation of volatile organic compounds (VOCs). Nevertheless, pure manganese oxides suffer from poor activity especially at low temperatures, making it difficult to meet industrial applications. In this work, Co species were successfully doped into the lattice of MnO2 aiming at constructing defects to boost its catalytic performance for VOCs oxidation. In combination with the results of systematic characterizations, we found that Co doping forced the catalyst to transform from α‐MnO2 to spinel phase (Co,Mn)(Co,Mn)2O4. During this process, the metal–oxygen bonds are significantly weakened, which induces the massive generation of oxygen defects, endowing the Co modified catalysts with enhanced redox property and improved ability to adsorb and activate gaseous oxygen. As a result, Co doped catalysts show much better catalytic activity compared with pristine α‐MnO2, among which Mn10Co10 exhibits the best performance showing a decrease of 41°C and 51°C in T50 and T90 compared with the raw sample, respectively. Furthermore, Mn10Co10 demonstrates excellent stability, water resistance, and reusability, illustrating a great potential for industrial applications. Moreover, path of toluene decomposition over Co10Mn10 was revealed by in situ DRIFTS experiment, which complies with the sequence of toluene → benzyl alcohol → benzaldehyde → benzoate → maleic anhydride → CO2 and H2O.

Highly Conductive Peroxidase-like Ce-MoS2 Nanoflowers for the Simultaneous Electrochemical Detection of Dopamine and Epinephrine.

The accurate and simultaneous detection of neurotransmitters, such as dopamine (DA) and epinephrine (EP), is of paramount importance in clinical diagnostic fields. Herein, we developed cerium-molybdenum disulfide nanoflowers (Ce-MoS2 NFs) using a simple one-pot hydrothermal method and demonstrated that they are highly conductive and exhibit significant peroxidase-mimicking activity, which was applied for the simultaneous electrochemical detection of DA and EP. Ce-MoS2 NFs showed a unique structure, comprising MoS2 NFs with divalent Ce ions. This structural design imparted a significantly enlarged surface area of 220.5 m2 g-1 with abundant active sites as well as enhanced redox properties, facilitating electron transfer and peroxidase-like catalytic action compared with bare MoS2 NFs without Ce incorporation. Based on these beneficial features, Ce-MoS2 NFs were incorporated onto a screen-printed electrode (Ce-MoS2 NFs/SPE), enabling the electrochemical detection of H2O2 based on their peroxidase-like activity. Ce-MoS2 NFs/SPE biosensors also showed distinct electrocatalytic oxidation characteristics for DA and EP, consequently yielding the highly selective, sensitive, and simultaneous detection of target DA and EP. Dynamic linear ranges for both DA and EP were determined to be 0.05~100 μM, with detection limits (S/N = 3) of 28 nM and 44 nM, respectively. This study shows the potential of hierarchically structured Ce-incorporated MoS2 NFs to enhance the detection performances of electrochemical biosensors, thus enabling extensive applications in healthcare, diagnostics, and environmental monitoring.

Unique κ-Ce2Zr2O8 Superstructure Promoting the NOx Adsorption-Selective Catalytic Reduction (AdSCR) Performance of the WO3/CeZrOx Catalyst.

Selective catalytic reduction of NOx by NH3 (NH3-SCR) for diesel emission control at low temperatures is still a great challenge due to the limit of the urea injection threshold and inferior SCR activity of state-of-the-art catalyst systems below 200 °C. Fabricating bifunctional catalysts with both low temperature NOx adsorption-storage capacity and medium-high temperature NOx reduction activity is an effective strategy to solve the issues mentioned above but is rarely investigated. Herein, the WO3/Ce0.68Zr0.32Ox (W/CZ) catalyst containing the κ-Ce2Zr2O8 pyrochlore structure was successfully developed by a simple H2 reduction method, not only showing superior NOx adsorption-storage ability below 180 °C but also exhibiting excellent NH3-SCR activity above 180 °C. The presence of the pyrochlore structure effectively increased the oxygen vacancies on the κ-Ce2Zr2O8-containing W/CZ catalyst with enhanced redox property, which significantly promoted the NOx adsorption-storage as active nitrate species below 180 °C. Upon NH3 introduction above 180 °C, the κ-Ce2Zr2O8-containing W/CZ catalyst showed greatly improved NOx reduction performance, suggesting that the pyrochlore structure played a vital role in improving the NOx adsorption-selective catalytic reduction (AdSCR) performance. This work provides a new perspective for designing bifunctional CeZrOx-based catalysts to efficiently control the NOx emissions from diesel engines during the cold-start process.

Construction of supramolecular S-scheme heterojunctions assisted by hydrogen bond subtle-tuning actuates highly efficient photocatalytic oxidation

Controllable fine-tuning of heterojunction interfaces at the atomic level represents a promising strategy for enhancing semiconductor photocatalytic performance. Herien, we propose a strategy to introduce hydrogen-bonded electron channels at the heterojunction interface to achieve rapid interfacial electron transfer. This S-scheme hydrogen-bonded supramolecular self-assembled H12SubPcB-OPhCH2COOH/Ag3PO4 semiconductor heterojunction exhibits efficient and stable photocatalytic degradation of a wide range of pharmaceuticals and personal care products. Experimental results and theoretical simulations demonstrate that the interface O-H⋅⋅⋅O hydrogen bond at the heterojunction generates an internal electric field, which provides the driving force for accelerated S-scheme charge transfer and enhanced redox properties. Furthermore, the combination of TDDFT calculations and synchronous illumination XPS has revealed that hydrogen bonding acts as a suction electron pump in the excited state, transferring electrons from Ag3PO4 to SubPc-2. These findings suggest that hydrogen-bonded supramolecular semiconductor can be used to develop high-performance photocatalytic materials for environmental remediation.

Enhanced redox properties of Gd-doped CeO2–TiO2 induced by oxygen vacancies and disordered structure

The redox properties of Gd-doped CeO2–TiO2 (xGd = 0.03, 0.09, and 0.15) was related to the oxygen defects and the local atomic structure. As the gadolinium doping concentration increased, a low-angle shift of the CeO2 (111) peak was observed. The EPR spectrum of the gadolinium-doped sample had an oxygen vacancy peak, indicating the oxygen vacancies induced by gadolinium. The O 1s core-level spectra showed that the ratio of oxygen vacancies gradually increased with the gadolinium doping concentration, and the Gd 4d and Ce 3d core-level spectra showed that Gd3+ reduced Ce4+ to Ce3+. An EXAFS analysis of the local atomic structures around Ce and Gd showed an increase in the Ce–O and Ce-(Ce,Gd) bond lengths and peak broadening occurred upon gadolinium doping, indicating bond disordering. The same Ce–O and Gd–O bond lengths suggested that the gadolinium was substituted for the cerium site. Surface chemisorption characterization was carried out by analyzing O2-TPD and H2-TPR profiles: the peaks for oxygen desorption and hydrogen reduction gradually shifted to lower temperatures as the dopant concentration increased. The quantities of desorbed oxygen and reduced hydrogen also increased. These enhanced redox properties resulted from disordered Ce3+-VO∙∙-Gd3+ acting as a surface active site, which promoted the redox reaction.

Development of Nanomedicine from Copper Mine Tailing Waste: A Pavement towards Circular Economy with Advanced Redox Nanotechnology

Copper, the essential element required for the human body is well-known for its profound antibacterial properties, yet salts and oxides of copper metals in the copper mine tailings are reported to be a big burden in the modern era. Among other copper oxides, CuO, in particular, is known to have beneficial effects on humans, while its slight nanoengineering viz., surface functionalization of the nanometer-sized oxide is shown to make some paradigm shift using its inherent redox property. Here, we have synthesized nanometer-sized CuO nanoparticles and functionalized it with a citrate ligand for an enhanced redox property and better solubility in water. For structural analysis of the nanohybrid, standard analytical tools, such as electron microscopy, dynamic light scattering, and X-ray diffraction studies were conducted. Moreover, FTIR and UV-VIS spectroscopy studies were performed to confirm its functionalization. The antibacterial study results, against a model bacteria (S. hominis), show that CuO nanohybrids provide favorable outcomes on antibiotic-resistant organisms. The suitability of the nanohybrid for use in photodynamic therapy was also confirmed, as under light its activity increased substantially. The use of CuO nanoparticles as antibiotics was further supported by the use of computational biology, which reconfirmed the outcome of our experimental studies. We have also extracted CuO nanogranules (top-down technique) from copper mine tailings of two places, each with different geographical locations, and functionalized them with citrate ligands in order to characterize similar structural and functional properties obtained from synthesized CuO nanoparticles, using the bottom-up technique. We have observed that the extracted functionalized CuO from copper tailings offers similar properties compared to those of the synthesized CuO, which provides an avenue for the circular economy for the utilization of copper waste into nanomedicine, which is known to be best for mankind.

Dimethyl Ether Oxidation over Copper Ferrite Catalysts

The depletion of fossil energy sources and the legislation regarding emission control demand the use of alternative fuels and rapid progression of aftertreatment technologies. The study of dimethyl ether (DME) catalytic oxidation is important in this respect, as DME is a promising clean fuel and at the same time a VOC pollutant present in the tail gases of industrial processes. In the present work, copper ferrite catalysts synthesized via the citrate complexation method have been evaluated in DME oxidation. N2-physisorption, XRD, H2-TPR, and XPS were employed for the characterization of the mixed oxide catalysts. The copper ferrite spinel phase was detected in all samples accompanied by a gradual decrease in the bulk CuO phase upon increase in iron content, with the latter never vanishing completely. The Fe0.67Cu0.33 catalyst exhibited the highest catalytic activity in DME oxidation, attaining approximately a 4-fold higher oxidation rate compared to the respective pure copper and iron oxides. The enhanced catalytic performance was attributed to the higher specific surface area of the catalyst and its enhanced redox properties. Highly dispersed copper species were developed owing to the formation of the spinel phase. DME-TPD/TPSR experiments showed that the surface lattice oxygen of the Fe0.67Cu0.33 catalyst can oxidize preadsorbed DME at a lower temperature than all other catalysts which is in agreement with the H2-TPR findings.

Exploring the effect of calcination temperature and sulphuric acid impregnation treatment on the NH3-SCR activity of cold-rolled sludge

In recent years, sulphate materials have received more and more attention because of high activity in the selective catalytic reduction of nitrogen oxides with ammonia (NH3-SCR). In this paper, a series of catalysts for NH3-SCR were prepared by sulphuric acid impregnation and calcination at different temperatures of cold-rolled sludge which main component is iron oxide. The performance of cold-rolled sludge catalyst was measured by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), temperature programmed-reduction of hydrogen (H2-TPR), temperature programmed desorption of ammonia (NH3-TPD) and X-ray photoelectron spectroscopy (XPS). It was demonstrated that the increase of iron sulphate and Fe3+ content can be observed in the cold-rolled sludge after sulfuric acid impregnation and low temperature calcination (300 ℃), which leads to the improvement of SCR denitration performance. The results show that 100% denitration conversion can be achieved at 280 °C via the modified cold-rolled sludge, with 94% of the performance was retained after the introduction of SO2 and H2O for 5 h. There are minor morphological structural changes in the catalyst, while the redox properties and acidity of the catalyst changed significantly after the treatment process of sulfuric acid impregnation and calcination. This means that the enhanced redox properties and acidity of the catalyst play a key role in improving the activity of NH3-SCR.

Polypyrrole-based adsorbents for Cr(VI) ions remediation from aqueous solution: a review.

Anthropogenic activities are principally responsible for the manifestation of toxic and carcinogenic hexavalent chromium (Cr(VI)) triggering water pollution that threatens the environment and human health. The World Health Organisation (WHO) restricts Cr(VI) ion concentration to 0.1 and 0.05 mg/L in inland surface water and drinking water, respectively. The available technologies for Cr(VI) ion removal from water were highlighted with an emphasis on the adsorption technology. Furthermore, the characteristics of several polypyrrole-based adsorbents were scrutinized including amino-containing compounds, biosorbents, graphene/graphene oxide, clay materials and many other additives with reported effective Cr(VI) ion uptake. This efficiency in Cr(VI) ions adsorption is attributed to enhanced redox properties, increased number of functional groups as well as the synergistic behaviour of the materials making up the composites. The Langmuir isotherm best described the adsorption processes with maximum adsorption capacities ranging from 3.40-961.50 mg/g. The regeneration of Cr(VI) ion-laden adsorbents was studied. Ion exchange, electrostatic attractions, complexation, chelation reactions with protonated sites and reduction were the mechanisms of adsorption. Nevertheless, there are limited details on comprehensive adsorbent regeneration studies to prolong robustness in adsorption-desorption cycles and utilization of the Cr(VI) ion-laden adsorbent in other areas of research to limit the threat of secondary pollution.

N/Ce doped graphene supported Pt nanoparticles for the catalytic oxidation of formaldehyde at room temperature

Pt catalysts with nitrogen-doped graphene oxide (GO) as support and CeO2 as promoter were prepared by impregnation method, and their catalytic oxidation of formaldehyde (HCHO) at room temperature was tested. The Pt-CeO2/N-rGO (reduced GO) with a mass fraction of 0.7% Pt and 0.8% CeO2 exhibited an excellent catalytic performance with the 100% conversion of HCHO at room temperature. Physicochemical characterization demonstrated that nitrogen-doping greatly increased the defect degree and the specific surface area of GO, enhanced the dispersion of Pt and promoted more zero-valent Pt. The synergistic effect between CeO2 and Pt was also beneficial to the dispersion of Pt. Nitrogen-doping promoted the production of more Ce3+ ions, generating more oxygen vacancies, which was conducive to O2 adsorption. As a result, the catalyst exhibited enhanced redox properties, leading to the best catalytic activity. Finally, an attempt to propose the reaction mechanism of HCHO oxidation has been made.

Disordered Structure and Enhanced Redox Properties of Gd-Doped Ceo2-Tio2 Induced by Oxygen Vacancies

Disordered Structure and Enhanced Redox Properties of Gd-Doped Ceo2-Tio2 Induced by Oxygen Vacancies

Insight into the promoting effect of support pretreatment with sulfate acid on selective catalytic reduction performance of CeO2/ZrO2 catalysts

In this paper, sulfated ZrO2 were synthesized via precipitation and impregnation method, and the promoting effects of support sulfation on selective catalytic reduction (SCR) performance of CeO2/ZrO2 catalysts were investigated. The results revealed that sulfated ZrO2 could significantly enhance the SCR activity of CeO2/ZrO2 catalysts in a wide temperature range. Especially when S/Zr molar ratio was 0.1, CeO2/ZrO2-0.1S catalyst exhibited a large operating temperature window of 251 ∼ 500 °C and its N2 selectivity was 100 % in the temperature range of 150 ∼ 500 °C. Moreover, CeO2/ZrO2-0.1S catalyst possessed a superior low-temperature activity over 0.1S-CeO2/ZrO2 catalyst. After exposing to 100 ppm SO2 for 15 h, a high NO conversion efficiency of CeO2/ZrO2-0.1S catalyst (90.7 %) could still be reached. The characterization results indicated that ZrO2 treated with a proper dosage of sulfate acid was beneficial to enlarge the specific surface area greatly. Sulfated ZrO2 was also in favor of promoting the transformation of CeO2 from crystalline state to highly-dispersed amorphous state, and inhibiting the transformation of ZrO2 from tetragonal to monoclinic phase. It could also enhance the total surface acidity greatly with an increase in both Brønsted acid sites and Lewis acid sites, thus significantly improving NH3 adsorption on catalyst surface. Besides, the promoting effect of support sulfation on SCR performance of CeO2/ZrO2 catalysts was also related with the enhanced redox property, higher Ce3+/(Ce3++Ce4+) ratio and abundant surface chemisorbed labile oxygen. The in-situ DRIFTS results implied that nitrate species coordinated on the surface of CeO2/ZrO2-0.1S catalyst could participate in the Selective catalytic reduction with ammonia (NH3-SCR) reactions at either medium or high temperature, suggesting that both Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms might be followed in SCR reactions.

Enhanced redox property of polymer blends containing liquid crystalline molecules and their application in electrochemical sensing

A series of thermoplastic polyester elastomer (TPEE) derivatives based on recycled polyethylene terephthalate (r-PET) and poly(tetramethylene glycol) together with differing amounts (n%, n = 0, 1, 3, and 5) of 1,6-hexanediamine (HDA) were prepared. Blending of the copolymer with a rod-like liquid crystal (4-cyano-3-fluorophenyl 4-ethylbenzoate (4CFE)), named TPEEn%-4CFE, was studied. Among them, the TPEE3%-4CFE mixture featured optimal blending, with liquid crystals well-connected with the HDA moieties in the TPEE framework through hydrogen-bonding interaction, according to X-ray and Fourier-transform infrared spectroscopy analyses. A packing diagram is proposed to illustrate the unique performance of TPEE3%-4CFE, attributed to the enhancement of π–π interactions. The polarized mesophase and morphology indicated favorable dispersion of liquid crystals in the TPEE matrix in TPEE3%-4CFE, which was applied successfully in electrochemical sensing for ascorbic acid for the first time. The TPEE3%-4CFE-modified carbon paste electrode sensor is a rapid-response sensor with high sensitivity of approximately 11.30 μA mM−1, a wide linear dynamic range of 0.181.26 μM, and a limit of detection of 0.4 mM–1.6 mM.

Promotion Effect of Chromium on the Activity and SO2 Resistance of CeO2–TiO2 Catalysts for the NH3-SCR Reaction

The Cr-doped CeO2–TiO2 catalysts (CrCeTi) were produced via a coprecipitation method and used for selective catalytic reduction (SCR). The CrCeTi catalyst has good catalytic performance and sulfur resistance. The results of X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), NH3-TPD, NO-TPD, X-ray photoelectron spectroscopy (XPS), and H2 temperature-programmed reduction (H2-TPR) suggested that the CrCeTi catalyst with high specific surface area (SSA), strong surface acidity, enhanced redox properties, and effective electron transfer (3Ce4+ + Cr3+ ↔ 3Ce3+ + Cr6+) were the important promotion factors for excellent SCR properties. The in situ diffuse reflectance infrared spectroscopy (DRIFTS) indicated that the incorporation of Cr could improve the adsorption capacity of nitrate and the activation capacity of NH3, which were conducive to enhancing the catalytic activity. The thermogravimetric analysis-mass spectrometry (TG-MS) confirmed that the doping of Cr reduced SO2 surface adsorption and promoted the decomposition of NH4HSO4 (ABS). Therefore, the CrCeTi catalyst showed excellent resistance to SO2 poisoning.

Catalytic combustion of methane conducted on La–B–O–C (B[dbnd]Co, Mn, Fe) composites: The effects of B-sites cation properties

The novel La–B–O–C composites were fabricated as catalysts for methane catalytic combustion at low temperature, and considering the effect of newly C–O bond on B-site ions as active sites, three metal ions (Co, Mn, Fe) were selected for experiment. XRD, N2-physisorption, XPS and H2-TPR measurements were used to characterize the physicochemical properties of catalysts, which showed that the newly established C–O–B bond reduced the ionic valence of the B-site, and the redox capacities were increased or decreased to different degrees, respectively. Catalytic tests showed that T50 of La–Co–C–O composites (LC-C) and La–Fe–C–O composites (LF-C) are 377 °C and 482 °C, much lower than that of unmodified catalyst, respectively. But T50 of La–Mn–C–O composites (LM-C) increases to 507 °C from 493 °C. The superior performance of LC-C could be attributed to the high oxygen vacancies and enhanced redox property, and the better performance of LF-C was mainly benefited from the increase in lattice oxygen. For LM-C, the sacrifice of Mn4+ weakened the catalytic activity. There are more obvious mechanistic differences for different B-site elements in the La–B–O–C. The study will bring innovative insights into the design of excellent composites catalysts for methane oxidation.

The Effect of Co Incorporation on the CO Oxidation Activity of LaFe1−xCoxO3 Perovskites

Perovskite oxides are versatile materials due to their wide variety of compositions offering promising catalytic properties, especially in oxidation reactions. In the presented study, LaFe1−xCoxO3 perovskites were synthesized by hydroxycarbonate precursor co-precipitation and thermal decomposition thereof. Precursor and calcined materials were studied by scanning electron microscopy (SEM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TG), and X-ray powder diffraction (XRD). The calcined catalysts were in addition studied by transmission electron microscopy (TEM) and N2 physisorption. The obtained perovskites were applied as catalysts in transient CO oxidation, and in operando studies of CO oxidation in diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). A pronounced increase in activity was already observed by incorporating 5% cobalt into the structure, which continued, though not linearly, at higher loadings. This could be most likely due to the enhanced redox properties as inferred by H2-temperature programmed reduction (H2-TPR). Catalysts with higher Co contents showing higher activities suffered less from surface deactivation related to carbonate poisoning. Despite the similarity in the crystalline structures upon Co incorporation, we observed a different promotion or suppression of various carbonate-related bands, which could indicate different surface properties of the catalysts, subsequently resulting in the observed non-linear CO oxidation activity trend at higher Co contents.

Catalytic nonthermal plasma using efficient cobalt oxide catalyst for complete mineralization of toluene

The remarkable rise in industrial utilization of volatile organic compounds has increased their presence in environmental matrices, which is a menace for human health. Conventionally, many technologies are in practice for constricting their escape to the environment. However, due to associated adverse health hazards, more efficient technique ensuring complete mineralization is inevitably demanded. In the current study, the degradation of toluene by post-plasma catalysis using cobalt-coupled (Co3O4–CoO) catalyst was studied. Firstly, a new starch-assisted synthesis route for cobalt coupling is presented. Secondly, the research finding of this study showed that the formed cobalt couple exhibited robust performance for toluene degradation up to 99%, which was attributed to their enhanced redox property and adsorbed oxygen content. This promotion in catalytic ability is due to intrinsically greater oxygen storage capacity of coupling. Additionally, the results of this study indicated that toluene degradation was increased significantly with higher input power, whereas, without catalyst application, nonthermal plasma (NTP) alone produced other VOCs as a result of toluene degradation and higher NO concentration at high input power and higher O3 at low input power. Furthermore, it could be concluded that NTP along with cobalt-coupled catalyst promotes toluene degradation, controls the production of all other VOCs and O3 and significantly reduced the production of NO concentration.