Catalytic Oxidation Research Articles

Preparation of CHS-Fe3O4@@ZIF-8 peroxidase-mimic with an ultra-thin hollow layer for ultrasensitive electrochemical detection of kanamycin.

Ahighly sensitive and selective electrochemical biosensor was developedfor the detection of kanamycin using a core-hollow-shell structured peroxidase-mimic nanozyme, CHS-Fe₃O₄@@ZIF-8. The synthesized CHS-Fe3O4@@ZIF-8 was characterized with scanning electron microscopy, transmission electron microscopy, andX-ray photoelectron spectroscopy. Itwasfound that the CHS-Fe3O4@@ZIF-8 exhibits excellent peroxidase-like activity due to its ultra-thin hollow layer. Besides, CHS-Fe3O4@@ZIF-8 functionalized with complementary chains of kanamycin aptamer was anchored to the electrode surface via complementary base pairing with the kanamycin aptamer. Upon the presence of kanamycin, a strand displacement reaction was triggered leading to a reduction in the number of the CHS-Fe3O4@@ZIF-8, which slowed down the catalytic reaction of the substrate 3,3',5,5' -tetramethylbenzidine (TMB) facilitated by CHS-Fe3O4@@ZIF 8. Differential pulse voltammetry (DPV) was employed to measure and record changes in peak current resulting from catalytic oxidation product formation (oxidation product of TMB). The electrochemical signal exhibited a linear relationship with logarithmic variations in kanamycin concentration within a range spanning from 10 to 8000pM and achieved an impressive detection limit as low as 7.52pM. Furthermore, successful detection of kanamycin content in serum samples using this sensor demonstrated its good specificity and reproducibility. These findings indicate that theconstructed electrochemical kanamycin sensor holds significant potential for practical applications. The biosensor demonstrated high selectivity, distinguishing kanamycin from other antibiotics, and exhibited good reproducibility, making it reliable for practical applications. The successful detection of kanamycin in serum samples further underscores the sensor's potential for real-world applications, particularly in monitoring antibiotic residues in food products and clinical diagnostics.

Degradation of Methylene Blue by Ozone Oxidation Catalyzed by the Magnetic MnFe2O4@Co3S4 Nanocomposite.

In this study, the MnFe2O4@Co3S4 magnetic nanocomposite was prepared by a two-step hydrothermal method and used to catalyze the ozone oxidation degradation of methylene blue. It was characterized by XRD, EDS, SEM, FT-IR, and XPS. The results showed that the introduction of Co3S4 made MnFe2O4 grow uniformly on Co3S4 nanosheets, which effectively prevented the agglomeration of MnFe2O4. Moreover, MnFe2O4 provided active sites and Mn3+/Mn2+ and Fe3+/Fe2+ cycles for the ozone oxidation process. Not only did Co3S4 provide the active site (Co2+/Co3+) for the ozone oxidation process but also its derived S2-/S22- accelerated the electron transfer rate on the surface of the material, thus improving the efficiency of catalytic ozone oxidation degradation of methylene blue. When the molar ratio of MnFe2O4 to Co3S4 was 6:3 (MnFe2O4@Co3S4-3), the catalytic ozone degradation efficiency of methylene blue was the best, which reached 93.55% in 12 min. The reactive oxygen species in catalytic ozonation degradation of MB were 1O2, O2.-, and ·OH. The MnFe2O4@Co3S4 magnetic nanocomposite is an efficient and stable O3 activator, which maintains high catalytic activity and low metal ion leaching after five cycles, indicating that it has a good application prospect in catalyzing ozone oxidation to degrade organic pollutants.

Asymmetric Pt1O4-Ov Dual Active Sites Induced by NbOx Clusters Promotes CO Synergistical Oxidation.

Pt/CeO2 single-atom catalysts are attractive materials for CO oxidation but normally show poor activity below 150 °C mainly due to the unicity of the originally symmetric Pt1O4 structure. In this work, a highly active and stable Pt1/CeO2 single-site catalyst with only 0.1 wt % Pt loading, achieving a satisfied complete conversion of CO at 150 °C, can be obtained through fabricating asymmetric Pt1O4-oxygen vacancies (Ov) dual-active sites induced by well-dispersed NbOx clusters. Specifically, the formation of new Ce-O-Nb interactions weakened the strength of the original Pt-O-Ce bond, thus transferring the originally near-perfect square-planar Pt1O4 into the distorted square-planar one, along with forming abundant Ov around the Pt site. Hence, the promoted CO activation on the asymmetric Pt1O4 structure and the facilitated dissociation of the O2 on the neighboring Ov site synergistically improved the CO catalytic oxidation performance. The fabrication of such asymmetric Pt1O4-Ov double-active sites was also active for the oxidation of other typical hydrocarbons pollutants such as C7H8 and C3H6 from exhaust gases, shedding light on engineering high-efficiency Pt-based oxidation catalysts for low-temperature environmental catalysis.

Nearly Barrierless Four-Hole Water Oxidation Catalysis on Semiconductor Photoanodes with High Density of Accumulated Surface Holes.

The sluggish water oxidation reaction (WOR) is considered the kinetic bottleneck of artificial photosynthesis due to the complicated four-electron and four-proton transfer process. Herein, we find that the WOR can be kinetically nearly barrierless on four representative photoanodes (i.e., α-Fe2O3, TiO2, WO3, and BiVO4) under concentrated light irradiation, wherein the rate-limiting O-O bond formation step is driven by accumulated surface photogenerated holes that exhibit a superior fourth-order kinetics. The activation energy is about 0.03 eV for the fourth-order kinetic pathway, which is quantitatively estimated by combining the Population model and Butler-Volmer model with the Eyring-like equation and is further confirmed by density functional theory calculations. The WOR rate under this condition shows more than 1 order of magnitude enhancement compared with that of first-, second-, or third-order kinetics. Focusing on α-Fe2O3, the accumulated high-density surface holes form adjacent FeV═O intermediates that effectively activate surface-adsorbed H2O molecules via the hydrogen-bonding effect, as revealed by operando Raman measurements and ab initio molecular dynamics simulations. This work discloses a systematic understanding of the internal relations between activation energy and reaction orders of surface holes for future WOR study.

Liquid-Phase Catalytic Oxidation of Cyclohexene and its Methyl Derivative with Hydrogen Peroxide into Aliphatic Hydroxy Aldehydes and Hydroxy Acids

Liquid-Phase Catalytic Oxidation of Cyclohexene and its Methyl Derivative with Hydrogen Peroxide into Aliphatic Hydroxy Aldehydes and Hydroxy Acids

Cooking Oil Fumes: A Comprehensive Review of Emission Characteristics and Catalytic Oxidation Strategies

Cooking Oil Fumes: A Comprehensive Review of Emission Characteristics and Catalytic Oxidation Strategies

Transition Metal Complexes Containing Selenium Ligands for Catalytic Reduction, Oxidation, and Hydrofunctionalization Reactions.

Transition metal-mediated catalytic reduction, oxidation, and hydrofunctionalization reactions are important organic reactions and are considered highly atom-economical. Owing to their unique properties, selenium ligated several transition metals-based complexes have been reported for several catalytic applications. This review presents the synthesis of various selenium-supported transition metal complexes and their catalytic applications in reduction, oxidation, N-alkylation of amines, and hydrofunctionalization reactions. Furthermore, we compare the catalytic activity of various organoselenium ligand-containing transition metal complexes and the replacement of selenium with other chalcogen elements.

Design and synthesis of Pt/TiO2 catalyst with abundant surface hydroxyl for formaldehyde oxidation.

Catalytic oxidation of formaldehyde (HCHO) is a highly effective method for indoor HCHO removal. However, many aspects of the catalytic mechanism remain unclear, making the optimization of catalysts largely empirical. Herein, we report a coupled experimental and computational study of Pt/TiO2 catalysts, with special focus on the functional roles of surface oxygen vacancies and hydroxyl groups in the catalytic oxidation of HCHO. DFT calculations combined with control experiments revealed that the formation of surface oxygen vacancies on TiO2 and their capability in facilitating H2O dissociation are strongly dependent on the exposed facets. Correlating these facet-dependent properties with the determined activity further indicated that the catalytic performance is directly related to the abundance of surface hydroxyl groups, rather than surface oxygen vacancies as commonly assumed. Guided by these insights, we employed a combination of facet-engineering and alkali metal modification strategies to design a potassium-modified Pt/TiO2 catalyst with predominantly exposed {100} facets (denoted as Pt/TiO2{100}-K). The Pt/TiO2{100}-K catalyst showed an impressively high mass-specific reaction rate of 105.7 μmol gPt-1 s-1, along with fairly good stability and moisture tolerance. Further investigations using in situ DRIFTS coupled with on-line GC provided additional insight into the reaction mechanism of HCHO oxidation over the Pt/TiO2{100}-K catalyst.

Design of bifunctional nitrogen-doped biochar with adsorption and catalytic oxidation capabilities for enhanced toluene emission control.

Volatile organic compounds (VOCs), such as toluene, are hazardous air pollutants that pose significant health and environmental risks. This study addresses remediation of toluene by developing a bifunctional nitrogen-doped biochar (NDB) activated with sodium hydroxide (NaOH), aimed at reducing toluene emissions through both adsorption and catalytic oxidation. A series of NDB samples were prepared via NaOH activation and pyrolysis at varying temperatures to optimize their adsorption capacity and catalytic performance. The results demonstrated that NaOH-activated NDB exhibits substantial mesopore volumes and excellent surface area, with adsorption performance highly dependent on surface area and catalytic performance strongly influenced by nitrogen species. The dynamic adsorption tests revealed that BUN-900 achieved an outstanding toluene adsorption capacity of 422.25 mg/g, attributed to its high specific surface area of 1321.72 m2/g. In contrast, BU-800 showed complete toluene conversion at 450 °C via catalytic oxidation, attributed to the presence of pyridinic-N species. Interestingly, while the sample with the best adsorption performance had the lowest catalytic oxidation performance, the sample with the best catalytic performance exhibited the lowest adsorption capacity. This study demonstrates that NaOH activation and nitrogen doping can significantly enhance the bifunctional properties of biochar, positioning it as a promising, sustainable material for VOC control through combined adsorption and catalytic oxidation.

Analysis of Deactivation Causes and Regeneration Study of RuO2 /TiO2 in Industrial Catalytic Wet Oxidation Process

Analysis of Deactivation Causes and Regeneration Study of RuO2 /TiO2 in Industrial Catalytic Wet Oxidation Process

Combination of FeII-O Species and Fe-O-Zr Bonds Empowers FeOx Nanoclusters Anchored on UiO-66 Robust H2S-Selective Catalytic Oxidation Performance.

The low sulfur selectivity of Fe-based H2S-selective catalytic oxidation catalysts is still a problem, especially at a high O2 content. This is alleviated here through anchoring FeOx nanoclusters on UiO-66 via the formation of Fe-O-Zr bonds. The introduced FeOx species exist in the form of FeIII and FeII. Therein the FeIII-O species are the predominant active sites for H2S-oxidation. The formed Fe-O-Zr bonds strengthen the redox cycle of FeIII/FeII through promoting electron transfer from Fe to Zr. The FeII-O species can activate molecular oxygen to oxidize H2S into elemental S, which accelerates the formation rate of atomic S, hindering its further oxidation into SO2. The combination of these factors empowers the catalysts, enabling 100% H2S conversion and 98.2% sulfur yield. The catalyst also has satisfactory stability with the sulfur selectivity only decreasing from 98.2% to 91.3% after the reaction going on 50 h. The decreased sulfur selectivity might be caused by the deterioration of pores and the deposition of elemental S on the surface. The former hinders the diffusion of sulfur oligomers timely from pores to the gas phase, while the latter is suspected to capture electrons to promote its further reaction with molecular oxygen.

Tandem Reaction on Ru/Cu-CHA Catalysts for Ammonia Elimination with Enhanced Activity and Selectivity.

Ammonia emissions from vehicles and power plants cause severe environmental issues, including haze pollution and nitrogen deposition. Selective catalytic oxidation (SCO) is a promising technology for ammonia abatement, but current catalysts often struggle with insufficient activity and poor nitrogen selectivity, leading to the formation of secondary pollutants. In this study, we developed a bifunctional Ru/Cu-CHA zeolite catalyst for ammonia oxidation, incorporating both SCO sites (Ru) and selective catalytic reduction sites (SCR, Cu). Various characterizations, including HAADF-STEM, XAFS, and H2-TPR, revealed that Cu2+ cations are dispersed within the CHA zeolite, while RuOx clusters and nanoparticles are present both inside and on the surface of the zeolite. Operando DRIFTS-MS, in situ Raman spectroscopy, and DFT calculations confirmed that NH3 adsorbed on Cu2+ Lewis acid sites efficiently reduced RuO2 with a lower energy barrier, significantly enhancing the low-temperature activity of the Ru/Cu-CHA catalyst. Additionally, Cu2+ cations further facilitated the elimination of byproducts (NOx) via the tandem SCR reaction, thus greatly improving the nitrogen selectivity. This synergistic effect contributed to high catalytic activity (>94% at 200 °C) and excellent nitrogen selectivity (>90% even at high temperatures above 325 °C) for Ru2.5/Cu-CHA during practical ammonia elimination in the presence of NOx and water vapor.

Ultrasmall α-MnO2 with Low Aspect Ratio: Applications to Electrochemical Multivalent-Ion Intercalation Hosts and Aerobic Oxidation Catalysts.

Hollandite-type α-MnO2 exhibits exceptional promise in current industrial applications and in advancing next-generation green energy technologies, such as multivalent (Mg2+, Ca2+, and Zn2+) ion battery cathodes and aerobic oxidation catalysts. Considering the slow diffusion of multivalent cations within α-MnO2 tunnels and the catalytic activity at edge surfaces, ultrasmall α-MnO2 particles with a lower aspect ratio are expected to unlock the full potential. In this study, ultrasmall α-MnO2 (<10nm) with a low aspect ratio (c/a ≈ 2) is synthesized using a newly developed alcohol solution process. This material demonstrates exceptional performance across various multivalent battery systems, primarily due to the significantly reduced cation diffusion distance. Notably, an ultrasmall α-MnO2-graphene composite achieves high capacity with low overpotential when paired with an F-free electrolyte in Ca battery. Regarding aerobic oxidation catalysis, the nanosizing of α-MnO2 has a profound impact on aerobic oxidation catalysis. The increased efficiency of oxidative conversion reactions, such as the oxidation of 1-phenylethanol, is attributed to the greatly expanded active surface area of the catalyst. The versatile functionality of ultrasmall α-MnO2 underscores its potential to revolutionize energy storage and catalysis, offering broad applicability in next-generation green energy technologies.

An Endothelium‐Mimicking, Healable Hydrogel Shield for Bioprosthetic Heart Valve with Enhanced Intravascular Biocompatibility

AbstractBioprosthetic heart valves (BHVs) for transcatheter replacement often face deterioration due to thrombosis, inflammation, and calcification, which are irreversible. Here, a multidimensional endothelium‐mimicking healable hydrogel shielded BHV that not only withstand the complex valvular physiological and hemodynamic environment but also able to reverse damage‐induced structural degeneration by in situ healing is proposed. Polydopamine/selenocystamine nanoparticles with photothermal effect are embedded to achieve light‐triggered healing and catalytic nitride oxide generation in polyvinyl alcohol hydrogel coating on BHV surface. Additionally, platelet inhibitor Tirofiban is encapsulated in the hydrogel shield to block acute coagulation cascade in early stage after implantation. A rodent intravascular leaflet‐like implantation model is developed to reveal the long‐term hemocompatibility of BHVs in abdominal aorta. The shielded BHVs exhibit enhanced antithrombotic properties, reduced inflammation, superior endothelialization, and improved vascular patency. Transcriptome analysis indicates better endothelial functions on shielded BHVs. Moreover, the endothelium‐mimicking hydrogel shield maintains both mechanical properties and biological functions after healing, facilitated great hemocompatibility and fast re‐endothelialization. Collectively, the multidimensional endothelium‐mimicking strategy provides new insight for preventing and reversing BHV damage instead of solely replacement.

Valorization of Humins by Cyclic Levulinic Acid Production Using Polyoxometalates and Formic Acid.

At a time when increasing attention is paid to sustainability in chemistry, levulinic acid (LA) is one of the most important platform chemicals for the goal of overcoming our dependence on fossil raw materials. In this work, a new catalytic route for the effective utilization of these humin byproducts, enabling a cyclic synthesis of LA using formic acid (FA) as organocatalyst is proposed. Selective catalytic oxidation (SCO) of humins using the H5PV2Mo10O40 (HPA-2) polyoxometalate (POM) catalyst produces FA that can be isolated from the aqueous reaction mixture by using nanofiltration membranes accompanied by a complete catalyst recycling (>99%). After concentration of formic acid by distillation, the latter can be used as organocatalyst for levulinic acid production from sugars, whereby the formed humins can in turn be separated and used as substrates for further FA production via SCO to close the catalytic cycle. By using FA as a green and sustainable acidic organocatalyst, relatively high yields of LA (up to 42 mol%) could be achieved.

Exhaust Treatment for Engines Operated with the Synthetic Diesel Fuel OME: Low‐Temperature Oxidation of Formaldehyde and CO by Pt/Ceria Catalysts

AbstractC1‐based synthetic fuels like oxymethylene ether (OME) are sulfur‐free, and their combustion forms negligible amounts of soot. This results in reduced ageing requirements and can enable the development of cost‐efficient catalyst technologies. This work focuses on the catalytic oxidation of formaldehyde (HCHO), which is increasingly formed during the combustion of C1‐based fuels such as OME, methanol, or CH4. The oxidation of HCHO on Pt/Al2O3 is inhibited by CO, so that in real exhaust containing CO and NO, full conversion of HCHO is only observed at ∼200 °C. The main discovery of this paper is that on Pt/ceria the oxidation of HCHO is not inhibited by CO, so that full conversion of HCHO is achieved already at ∼100 °C even in the presence of CO. To demonstrate the performance of the new catalyst under realistic operating conditions, a dynamic HCHO dosing unit was developed, allowing to reproduce transient vehicle driving cycles on a lab‐scale test rig. Using this novel setup, the Pt/ceria catalyst shows virtually full conversion of HCHO (99,8%) and CO (98,5%) over an OME cold‐start driving cycle, where the conventional Pt/Al2O3 oxidation catalyst with four‐times higher Pt loading shows only 81% and 62% conversion, respectively.

Low-temperature catalytic oxidation of ethanol over doped nickel phosphates.

This work is focused on the synthesis and performance of Ni3(PO4)2-based catalysts doped with Cu, Co, Mn, Ce, Zr, and Mg for the complete oxidation of ethanol, aiming at reducing emissions from ethanol-blended gasoline. Nickel phosphate was prepared via the co-precipitation method, followed by impregnation with the specified dopants. The catalysts were thoroughly characterized by XRD, N2-physisorption, XRF, FTIR and Raman spectroscopy, FESEM, NH3-TPD, CO2-TPD, and H2-TPR to explain their performance. All catalysts achieved complete ethanol conversion (100%) at a temperature below 320°C. The performance of the catalysts was strongly influenced by the dopant type of which Co, Ce, Mn, and Mg showed high CO2 selectivity (selectivity > 90% at 95% ethanol conversion temperature (T95)). The mechanism of oxidation is affected by the acido-basicity of the catalysts and the redox properties leading to a reaction through ethylene formation over the acid catalysts and acetaldehyde over the basic catalysts. The redox properties of the doped catalysts play a crucial role in enhancing the catalytic activity and selectivity toward CO₂, as the redox-active dopants facilitate the activation of oxygen species, which are essential for the complete oxidation of ethanol. In particular, Co and Ce demonstrated superior redox characteristics, facilitating the conversion of intermediate species and leading to higher CO2 selectivity while minimizing undesirable by-products.

Development of Novel Monolithic Catalyst for BTEX Catalytic Oxidation Using 3D Printing Technology

Four differently shaped monolithic catalyst supports were made using 3D printing technology. Two catalytically active mixed oxides, MnFeOx and MnCuOx, were applied to the monolithic supports using the impregnation technique. Catalysts were characterized using an adhesion test, field emission scanning electron microscopy, X-ray diffraction, and Raman spectroscopy in a manner similar to the density functional theory model. Excellent mechanical stability of the catalyst layer was obtained, with catalyst mass loss under 2% after 30 min of ultrasound exposure. SEM analysis revealed that the catalyst layer was rough but homogeneous in appearance and ~6 μm thick. The presence of double oxides—FeMnO3 and CuMn2O4—as well as single oxides of Mn, Fe, and Cu was established via XRD and Raman spectroscopy. Additional theoretical calculations of Raman spectra for FeMnO3 and CuMn2O4 were performed in order to aid in the interpretation of Raman spectra. The catalytic activity of the prepared catalysts for the catalytic oxidation of a gaseous mixture of benzene, toluene, ethylbenzene, and o-xylene (BTEX) was investigated. The monolithic support with the most complex shape and, consequently, the greatest surface area proved to enable the highest efficiency, while both catalysts performed well having similar conversions.

Striking Improvement of N2 Selectivity in NH3 Oxidation Reaction on Fe2O3-Based Catalysts via SiO2 Doping.

The emission of NH3 has been reported to pose a serious threat to both human health and the environment. To efficiently eliminate NH3, catalysts for the selective catalytic oxidation of NH3 (NH3-SCO) have been intensively studied. Fe2O3-based catalysts were found to exhibit superior NH3 oxidation activity; however, the low N2 selectivity made it less attractive in practical applications. In this work, aimed at improving the N2 selectivity on Fe2O3-based catalysts, a simple SiO2 doping strategy was proposed. Although the NH3 oxidation activity showed almost no change on Fe2O3 after SiO2 doping, the N2 selectivity was significantly improved. Systematic characterizations revealed that SiO2 doping could increase the specific surface area of Fe2O3, and a strong interaction of Fe-O-Si was formed in Fe2O3-SiO2 mixed oxide catalysts. Furthermore, abundant Brønsted acid sites were formed on Fe2O3-SiO2 catalysts due to the facile hydrolysis of the Fe-O-Si structure into Si-OH and Fe-OH. Although SiO2 doping was found to weaken the redox ability of Fe2O3, the abundant Brønsted acid sites on Fe2O3-SiO2 catalysts could facilitate NH3 oxidation reaction through an internal SCR (i-SCR) pathway, thus achieving superior N2 selectivity. This work can provide new insights into constructing efficient NH3-SCO catalysts with high N2 selectivity.

Catalytic oxidation of 1,2-dichloroethane over CrOx/Co3O4 catalysts by incorporating CrOx into ZIF-67 derived Co3O4

Catalytic oxidation of 1,2-dichloroethane over CrOx/Co3O4 catalysts by incorporating CrOx into ZIF-67 derived Co3O4