Catalytic Activity For Oxidation Research Articles

Dual Nonradical Catalytic Pathways Mediated by Nanodiamond-Derived sp2/sp3 Hybrids for Sustainable Peracetic Acid Activation and Water Decontamination.

Peracetic acid (PAA) oxidation catalyzed by metal-free carbons is promising for advanced water decontamination. Nevertheless, developing reaction-oriented and high-performance carbocatalysts has been limited by the ambiguous understanding of the intrinsic relationship between carbon chemical/molecular structure and PAA transformation behavior. Herein, we comprehensively investigated the PAA activation using a family of well-defined sp2/sp3 carbon hybrids from annealed nanodiamonds (ANDs). The activity of ANDs displays a volcano-type trend, with respect to the sp2/sp3 ratio. Intriguingly, sp3-C-enriched AND exhibits the best catalytic activity for PAA activation and phenolic oxidation, which is different from persulfate chemistry in which the sp2 network normally outperforms sp3 hybridization. At the electron-rich sp2-C site, PAA undergoes a reduction reaction to generate a reactive complex (AND-PAA*) and induces an electron-transfer oxidation pathway. At the sp3-C site adjacent to C═O, PAA is oxidized to surface-confined OH* and O* successively, which ultimately evolves into singlet oxygen (1O2) as the primary reactive species. Benefiting from the dual nonradical regimes on sp2/sp3 hybrids, AND mediates a sustainable redox recycle with PAA to continuously generate reactive species to attack water contaminants, meanwhile maintaining structural/chemical integrity and exceptional reusability in cyclic runs.

Catalytic promiscuity, cytotoxicity and protein cleavage mediated by mononuclear copper(II) complexes: oxidative and hydrolytic activities

In this work, we describe the synthesis and structural and spectroscopic characterizations of two copper(II) complexes, [(Cu)(L1)(Cl2)].4H2O (1), where L1 is 2-(pyridin-2-yl)-1,3-bis(pyridin-2-ylmethyl)-hexahydropyrimidine, and [Cu(L2)](ClO4)2 (2), where L2 is N1,N1,N3-tris(pyridin-2-ylmethyl)propane-1,3-diamine. The crystalline structure analysis indicates that both complexes are mononuclear and pentacoordinated compounds. In the case of complex 1, it bears a neutral charge, with the ligand coordinating to the Cu(II) center in a tridentate manner, utilizing N-donor atoms. Additionally, two cis-chlorido ligands completing the coordination sphere. On the other hand, complex 2 is a cationic complex, with the ligand coordinated in a pentadentate manner, with only N-donor atoms for coordination around the Cu(II). Complex 1 showed catalytic promiscuity, displaying hydrolytic and oxidative activity. The hydrolytic activity was investigated using bis(2,4-dinitrophenyl) phosphate (2,4-BDNPP) as a phosphodiester substrate and applying the Michaelis–Menten approach, obtaining the following kinetic parameters: kcat = 1.21 × 10-4 s−1; KM = 3.35 × 10-3 molL-1. Complex 1 also accelerates the oxidation of the 3,5-di-tert-butylcatechol (3,5-DTBC) substrate with catalytic efficiency equal to 6.11 L mol-1s-1. Interestingly, we demonstrated that this Cu(II) complex 1 can also cleave the very stable peptide bonds from BSA (bovine serum albumin) through an oxidative mechanism using ascorbate as a reducing agent. Complexes 1 and 2 show good cytotoxic activity against two cancer cell lines: A431 from human squamous cell carcinoma and K562 from chronic myeloid leukemia. This study showed that complexes 1 and 2 are selective towards cancer cells.

Unlocking the superior flexibility and enhanced catalytic oxidation performance of CoTiO3 nanofibrous membranes through zirconium doping

The development of continuous CoTiO3 (CTO) fibers with prominent catalytic oxidation activity, tunable fibrous structures, and improved recyclability is appealing for application in efficient organic wastewater treatment; however, inescapable flaws remain, such as their inherent brittleness and adverse operability. Herein, a facile and effective strategy is proposed for the fabrication of flexible and mechanically robust CTO nanofibrous membranes through a combination of element doping and sol–gel-assisted electrospinning. Compared with pristine CTO fibers, the resulting zirconium-doped CoTiO3 (ZCTO) nanofibrous membranes displayed remarkably enhanced flexibility and tensile mechanics, which were attributed to their lower crystallinity, smaller grain size, and fewer fiber surface defects. The developed ZCTO fibrous membrane demonstrated exceptional resistance to bending fatigue, retaining a polymer-like bending rigidity of approximately 25 mN even after undergoing 200 reciprocating bending cycles. Furthermore, the incorporation of zirconium into CTO clearly had an advantageous effect on the formation of oxygen vacancies, thereby enhancing the surface adsorption of peroxymonosulfate (PMS), accelerating the electron transfer process, and weakening the peroxy bonds. The tetracycline degradation efficiency of the ZCTO fibers remained at 81.4% within 10 min after 5 continuous cycles. Benefiting from their robust mechanical properties and excellent catalytic activity, the fabricated membranes demonstrated outstanding dynamic catalytic performance under gravity-driven conditions. More importantly, the reported strategy might be adopted and extended to develop a wide range of ceramic fibers with enhanced flexibility and mechanics for catalytic oxidation.

Solvent-Free Synthesis Enables Encapsulation of Subnanometric FeOx Clusters in Pure Siliceous Zeolites for Efficient Catalytic Oxidation Reactions.

Metal/metal oxide clusters possess a higher count of unsaturated coordination sites than nanoparticles, providing multiatomic sites that single atoms do not. Encapsulating metal/metal oxide clusters within zeolites is a promising approach for synthesizing and stabilizing these clusters. The unique feature endows the metal clusters with an exceptional catalytic performance in a broad range of catalytic reactions. However, the encapsulation of stable FeOx clusters in zeolite is still challenging, which limits the application of zeolite-encapsulated FeOx clusters in catalysis. Herein, we design a modified solvent-free method to encapsulate FeOx clusters in pure siliceous MFI zeolites (Fe@MFI). It is revealed that the 0.3-0.4 nm subnanometric FeOx clusters are stably encapsulated in the 5/6-membered rings intersectional voids of the pure siliceous MFI zeolites. The encapsulated Fe@MFI catalyst with a Fe loading of 1.4 wt % demonstrates remarkable catalytic activity and recycle stability in the direct oxidation of methane, while also promoting the direct oxidation of cyclohexane, surpassing the performance of conventional zeolite-supported Fe catalysts.

In situ exsolution of Pt nanoparticles on low Pt-substituted A-site deficient perovskite for efficient CO oxidation

Platinum nanoparticles often lose their efficacy in challenging working environments. In this study, we developed a novel approach for the preparation of highly dispersed precious metal catalysts. The method involves the utilization of composite materials consisting of PtOx/(LC)0.9MP, achieved through the exsolution of a low Pt substituted A-site deficient perovskite (La0.97Ce0.03)0.9Mn0.99Pt0.01O3 ((LC)0.9MP). This procedure facilitates the in situ exsolution of Pt nanoparticles from (LC)0.9MP through heat treatment under 10 vol% H2/Ar environment. During this process, PtOx undergoes transformation to Pt0, exhibiting a high CO catalytic oxidation activity, with the T100(CO) decreasing from 213 to 141 °C. This capability primarily stems from the substantial number of oxygen vacancies and alterations in Pt species induced by the catalyst during the redox process. The active Pt nanoparticles are strongly integrated on the surface of (LC)0.9MP, demonstrate excellent CO oxidation activity and stability. This performance is attributed to the specific structure of perovskite. Upon reoxidation, these particles do not undergo direct reincorporation into the lattice structure. Instead, NPs result in the formation of stable, anchored oxide nanoparticles. This strategy can be extended to other metals oxides catalysts, thus may help the rational design of highly efficient transition metal oxide-based catalysts and beyond.

Effect of cobalt on CeO2 nanorod supported Pt catalyst: Structure, performance, kinetics and reaction mechanism in CO oxidation

Catalytic oxidation represents a highly efficient and extensively employed approach for the elimination of CO in exhaust gas. Rationally designing and preparing catalysts with exceptional activity and stability in the presence of H2O and SO2 at low temperatures represent crucial avenues for future advancements. In this work, a series of Pt catalysts supported on CeO2 nanorods incorporated with varying amounts of Cobalt (Co/CeO2 ratio ranging from 0 to10) were prepared and evaluated for their catalytic activity in CO oxidation under both dry and wet conditions. The ultrahigh dispersion of Pt, outstanding redox properties, and abundant oxygen vacancies on the surface of Co-doped CeO2 nanorod supported Pt catalysts were revealed by XRD, HAADF-STEM, Raman spectroscopy and H2-TPR techniques. The catalytic activity for CO oxidation strongly depends on the Co content and reaction conditions. Among them, Pt/Co-CeO2-5 % exhibits the highest CO oxidation performance with a T90 (the temperature to achieve 90 % conversion of CO) of 170 °C under dry conditions, which is significantly lower by 140 °C compared to T90 of Pt/CeO2. Pt/Co-CeO2-1 % demonstrates superior CO oxidation performance with a T90 of 195 °C under wet conditions, exhibiting a reduction in temperature by 65 °C compared to the T90 of Pt/CeO2. Moreover, Pt/Co-CeO2 exhibits excellent resistance to SO2 compared to Pt/CeO2. Kinetic studies, in situ DRIFT analysis and isotopic experiments demonstrated direct participation of H2O in the reaction. On the catalysts with a low Co/Ce ratio (Co/Ce < 0.03), CO readily reacts with hydroxyl groups dissociated from H2O to form carboxyl intermediates, which subsequently undergo rapid decomposition into CO2, resulting in an enhanced reaction rate of CO oxidation at low temperature.

Supported palladium nanocubes reduced by graphene oxide and surface-cleaned for enhanced electrocatalytic activity

Highly dispersed Pd nanocubes (Pd NCs) supported on the surface of partially reduced graphene oxide (pRGO) were successfully prepared by a facile procedure. GO was used as reductant and support without any other external reducing agent been introduced, and potassium iodide (KI) was used as capping agent for morphology control respectively. Catalytic activities for ethanol oxidation and methanol oxidation were greatly enhanced after excess iodine on the surface of Pd NCs was removed by being surface-treated with NaBH4 solution.

Boosting catalytic oxidation of propane over CeO2-supported Co3O4 catalyst with strong interfacial interaction and electron transfer

Tuning the nanoparticle-support interaction can optimize the catalytic performance of supported metal oxide catalysts for VOCs removal. Herein, a series of Co3O4/CeO2 catalysts with different strengths of interfacial interaction and electron transfer were successfully constructed via various modified wetness impregnation procedures. With the introduction of ammonium hydroxide, citric acid or H2 pretreatment, a stronger interfacial interaction and electron transfer were achieved due to the highly Co3O4 dispersion and CeO2 surface reconstruction. The modified-synthesis Co3O4/CeO2 catalysts, particularly Co3O4/CeO2-CA (citric acid), demonstrated superior catalytic activity (T90 = 296 °C, TOF = 0.337 × 10−3 s−1) and stability for propane oxidation as compared to typical wetness impregnation Co3O4/CeO2-DI (T90 = 314 °C, TOF = 0.121 × 10−3 s−1). Through systematic characterizations and DFT calculation, the strong interfacial interaction and abundant reactive oxygen species facilitate the adsorption and activation of C3H8 and O2 on the catalyst surface, which further promote the intermediates (carbonate/carboxyl species) transformation. These findings highlight interfacial mechanism to catalytic performance optimization of supported metal oxides.

Metallophthalocyanine as ideal antibiotics without light: Mechanisms and applications

The urgent global health problem of antimicrobial resistance (AMR) calls for the discovery of new antibiotics with innovative modes of action while considering the low toxicity to mammalian cells. This paper proposes a novel strategy for designing antibiotics with selective bacterial toxicity by exploiting the positional differences of electron transport chains (ETC) in bacterial and mammalian cells. The focus is on cytochrome c (cyt C) and its maturation system in E. coli. The catalytic oxidative activity of metallophthalocyanine (MPc), which have a distinctive M-N4 structure, is being investigated. Unlike previous applications based on light-activated reactive oxygen species (ROS) generation, this study exploits the ability of MPcs to oxidize Fe2+ to Fe3+ in cyt C and catalyze the formation of disulfide bonds between cysteine residues to interfere with cyt C maturation, disrupt the bacterial respiratory chain and selectively kills bacteria. In contrast, in mammalian cells, these MPcs are located in the lysosomes and cannot access the ETC in the mitochondria, thus achieving selective bacterial toxicity. Two MPcs that showed effective antibacterial activity in a wound infection model were identified. This study provides a valuable reference for the design of novel antibiotics based on M-N4-based metal complex molecules.

Catalytic Oxidation of Chlorobenzene over Amorphous Manganese-Chromium Catalysts Supported by UiO-66-Derived ZrOx.

The development of efficient catalysts with longevity to remove chlorobenzene is challenging due to Cl poisoning. Herein, a series of Mn-Cr/ZrOx catalysts supported by Zr-based metal-organic framework (UiO-66)-derived ZrOx was prepared and investigated for chlorobenzene (CB) catalytic oxidation. MnCr/ZrOx-M prepared via a wet impregnation method presented an amorphous structure, indicating the homogeneous dispersion of Cr and Mn, which improved acid and redox properties. 40Mn7Cr3/ZrOx-M exhibited the best catalytic activity for chlorobenzene oxidation with T90 of 293 °C, which is mainly due to the strong interaction between manganese and chromium promoted by the large specific surface area of the ZrOx support. Furthermore, 40Mn7Cr3/ZrOx-M presented excellent stability for chlorobenzene oxidation.

Facile construction and enhanced catalytic activity of Co-Mn oxide with rich amorphous/crystalline interfaces for propane oxidation

Cobalt-manganese (Co-Mn) composite oxides show high potential for the catalytic oxidation of volatile organic compounds (VOCs). However, the low defect content and poor oxygen mobility of perfect spinel structure crystalline always make it difficult to effectively activate C–H bonds of propane. Here, the catalyst with rich amorphous MnOx/crystalline Co3O4 interfaces was prepared, and the catalytic combustion activity for propane was determined. The rich amorphous/crystalline interfaces CMO-400 (i.e. Co-Mn oxide calcined at 400 °C) catalyst exhibited the best catalytic activity for propane with T90 of 200 °C among all bimetallic Co-Mn oxides. Various characterizations and corresponding results have demonstrated that the abundant amorphous/crystalline interfaces could improve the catalytic performances, attributed to high oxygen vacancy concentration, low temperature reducibility, weak Mn−O bond strength, and good surface lattice oxygen mobility. It is noteworthy that the interface engineering of amorphous/crystalline is an effective strategy in VOCs catalytic oxidation.

Sn-based precursors dependence for electrocatalytic degradation of organic pollutants on Ti/SnO2-Sb electrode

The utilization of SnO2-based coated electrodes prepared through thermal decomposition process for degrading organic pollutants is a prominent topic in the field of wastewater treatment. However, the impact of precursor salts on the structure and catalytic degradation activity of Sn oxide coatings still lacks research. This study examined the procedures for synthesizing SnO2 coatings by high-temperature oxidation of two common Sn chlorides with different valences. Through systematic characterization, it was revealed that the high boiling point of SnCl2 makes it less volatile during the high-temperature oxidation stage, allowing for maximum retention of Sn source on the substrate, thereby forming a dense and stable oxide coating structure (Ti/SnO2-Sb(II)). On the other hand, the low boiling point of SnCl4 makes it easily volatile during heating, resulting in a thin and loose structure coating (Ti/SnO2-Sb(IV)). Due to these factors that the electrical conductivity of Ti/SnO2-Sb(II) is significantly superior to Ti/SnO2-Sb(IV). Moreover, at 20 mA·cm−2, Ti/SnO2-Sb(II) can achieve almost complete decolorization of methylene Blue (MB) in just 40 minutes, while achieving the same decolorization rate with Ti/SnO2-Sb(IV) requires over 90 minutes. Furthermore, stability tests demonstrated that after 5 cycles of reaction, Ti/SnO2-Sb(II) showed no significant decrease in decolorization rate of MB, whereas Ti/SnO2-Sb(IV) exhibited a decline in decolorization performance towards MB starting from the 2nd cycle. This study revealed the crucial role of precursor salt boiling points in the formation of stable SnO2-based coated electrodes, providing a theoretical basis for the development of structurally stable and highly catalytic oxidation active coating electrodes.

Modulating the anchoring states of Ag on TiO2 by SiO2 to boost the NH3-SCO activity over Ag-based catalysts

Ag-based catalysts show high activity in NH3-selective catalytic oxidation (NH3-SCO). The anchoring states of Ag species determines its valence and dispersion, thereby influencing the performance of Ag-based catalysts. Herein, we elucidated that the content and anchoring strength of the hydroxyl (OH) groups on support together affect the anchoring states of Ag. TiO2 has few OH groups but high anchoring strength, the anchored Ag is in a highly dispersed oxidized state, while the unanchored Ag is aggregated in a metallic state (Ag0), so it presents an unevenly sized dispersion and mainly in oxidized state. SiO2 has abundant OH groups but weak anchoring, and can excessively agglomerate into large Ag0 nanoparticles (Ag0 NPs). Therefore, the introduction of SiO2 can regulate the anchoring states of Ag on the TiO2 support, making Ag presents highly dispersed Ag0 NPs, thus following a reaction mechanism with lower energy barriers and significantly improving the NH3-SCO performance.

Breaking Continuously Packed Bimetallic Sites to Singly Dispersed on Nonmetallic Support for Efficient Hydrogen Production.

We have synthesized Pt1Zn3/ZnO, also termed 0.01 wt %Pt/ZnO-O2-H2, as a catalyst containing singly dispersed single-atom bimetallic sites, also called a catalyst of singly dispersed bimetallic sites or a catalyst of isolated single-atom bimetallic sites. Its catalytic activity in partial oxidation of methanol to hydrogen at 290 °C is found to be 2-3 orders of magnitude higher than that of Pt-Zn bimetallic nanoparticles supported on ZnO, 5.0 wt %Pt/ZnO-N2-H2. Selectivity for H2 on Pt1Zn3/ZnO reaches 96%-100% at 290-330 °C, arising from the uniform coordination environment of single-atom Pt1 in singly dispersed single-atom bimetallic sites, Pt1Zn3 on 0.01 wt %Pt/ZnO-O2-H2, which is sharply different from various coordination environments of Pt atoms in coexisting PtxZny (x ≥ 0, y ≥ 0) sites on Pt-Zn bimetallic nanoparticles. Computational simulations attribute the extraordinary catalytic performance of Pt1Zn3/ZnO to the stronger adsorption of methanol and the lower activation barriers in O-H dissociation of CH3OH, C-H dissociations of CH2O to CO, and coupling of intermediate CO with atomic oxygen to form CO2 on Pt1Zn3/ZnO as compared to those on Pt-Zn bimetallic nanoparticles. It demonstrates that anchoring uniform, isolated single-atom bimetallic sites, also called singly dispersed bimetallic sites on a nonmetallic support can create new catalysts for certain types of reactions with much higher activity and selectivity in contrast to bimetallic nanoparticle catalysts with coexisting, various metallic sites MxAy (x ≥ 0, y ≥ 0). As these single-atom bimetallic sites are cationic and anchored on a nonmetallic support, the catalyst of singly dispersed single-atom bimetallic sites is different from a single-atom alloy nanoparticle catalyst. The critical role of the 0.01 wt %Pt in the extraordinary catalytic performance calls on fundamental studies of the profound role of a trace amount of a metal in heterogeneous catalysis.

Comparative study of Mn oxide catalysts on toluene oxidation: The effect of Mn valence electronic structures

Understanding the structure-activity relationship of Mn-based oxide catalysts is of great importance for the rational development of highly performance catalysts for VOCs catalytic oxidation. However, the knowledge of the electronic structure-catalytic oxidation activity relationship over Mn-based oxide catalysts is still limited. Herein, we investigated the typical MnxOy (Mn3O4, MnO2, and Mn2O3) with different valence electronic structures by using various characterizations and DFT calculations. The MnO2 exhibits superior intrinsic activities (RS, 1.14×10−9 mol·m−2·s−1) when compared with Mn3O4 (0.54×10−9 mol·m−2·s−1) and Mn2O3 (0.45×10−9 mol·m−2·s−1) for toluene catalytic oxidation. The solid experimental and DFT calculation results show that the d-band center of Mn determines the intrinsic activity. The superior catalytic oxidation activity of MnO2 can be attributed to its higher d-band center (-1.03 eV) in comparison with that of Mn3O4 (-1.25 eV) and Mn2O3 (-1.59 eV). The higher d-band center can weaken the surface Mn-O bonds strength (k = 290.9 N/m) and strengthen the gaseous O2 adsorption simultaneously, then enhancing the mobility of surface lattice oxygen and the amount of adsorbed oxygen species. This work firstly reveals the intrinsic relationship between catalytic oxidation activity and d electronic structure over Mn-based oxide catalysts and provides knowledge that will advance the design of high-performance catalysts for catalytic oxidation.

Morphology effect of cerium dioxide on the catalytic performance of Ru/CeO2 catalyst for the oxidation of different CVOCs

CeO2 with different morphology of rod-shape (R-CeO2), cube-shape (C-CeO2) and octahedra-shape (O-CeO2) were synthesized as supports and impregnated with Ru to obtain Ru/CeO2 catalysts, and the performance of which in catalytic oxidation of different chlorine-containing volatile organic compounds (CVOCs) (1,2-dichloroethylene (DCE) and vinyl chloride (VC)) were investigated. Due to the stronger interaction between Ru and R-CeO2, Ru was highly dispersed on R-CeO2 and more Ru entered support lattice to form Ru-O-Ce structure, thus Ru/R-CeO2 catalyst exhibited better redox property. Ru addition enhanced the acidity of Ru/R-CeO2 and Ru/C-CeO2, while that of Ru/O-CeO2 decreased instead. The acidity mainly affected DCE catalytic activity when catalyst had sufficient redox property and chlorine resistance. Run+ content was the main factor affecting VC catalytic activity. Ru/R-CeO2 catalyst exhibited the best catalytic activity in both DCE and VC catalytic oxidation with T50 of 285 °C and 207 °C, respectively, due to its excellent redox property, acidity, and sufficient Run+. In situ DRIFTS suggested that DCE was first dissociated to VC and then oxidized to carboxylates, and the addition of Ru led to the oxidation of carboxylates to carbonyl and ultimately to complete oxidation to CO2 and H2O. Run+ was important for the oxidation of carboxylate intermediates.

Design and optimization of CuCo-LDO catalysts via ZIF-67 sacrificial templates for enhanced toluene oxidation: A comprehensive study on morphology, structure, and catalytic activity

The investigation into the development of an active transition-metal oxide catalyst with controllable morphology for the degradation of volatile organic compounds (VOCs) is a subject of considerable importance and warrants further exploration. In this study, ZIF-67 was prepared and employed as a sacrificial template, with varying quantities of Cu ions incorporated to synthesize layered copper-cobalt double oxide (CuCo-LDO) featuring a modifiable surface state. A comprehensive characterization of the CuCo-LDO catalysts was conducted, encompassing structural properties, morphology, surface chemical state, and redox properties, utilizing a range of analytical techniques. Subsequent evaluations included testing the catalytic activity for toluene oxidation and assessing stability performance. The results revealed that differing Cu contents played a pivotal role in inducing changes in the morphology and structure of CuCo-LDO, thereby significantly influencing its oxidation activity towards toluene. Notably, the flower-like structure of 3CuCo-LDO (Cu% = 20.14 wt.%) exhibited outstanding toluene oxidation activity attributable to its unique structure and composition. This research contributes novel insights to the design of highs-performance catalysts targeting volatile organic compounds.

V-doped MoO3 nanorods for highly selective oxidation of 5-hydroxymethylfurfural to bio-monomer 2, 5-furandicarboxylic acid

2,5-Furanodicarboxylic acid (FDCA) is a significant chemical derived from biomass and holds the potential to replace traditional petrochemicals in the production of biodegradable polyester materials. In this study, a series of new-type V-doped MoO3 catalysts with different crystalline phases were prepared through the hydrothermal method. The V-doped α-MoO3 with growth along the [010] crystal plane demonstrated the most efficient catalytic activity in the selective oxidation of 5-hydroxymethylfurfural (HMF) to produce FDCA, potentially attributable to the [010] crystal plane's superior affinity for substrate interactions. The catalysts were analyzed using TEM, XPS, XRD, FT-IR, N2 adsorption isotherms and other characterization techniques. The Box-Behnken response surface method was utilized to investigate and successfully determine the optimal reaction conditions. A remarkable HMF conversion of 99.5% and a 97.4% selectivity toward FDCA were achieved at 80 °C after 10 h using tert-butanol as the solvent and tert-butyl hydroperoxide as the oxidant. Furthermore, the catalyst could be readily recovered conveniently and reused without any significant loss in catalytic activity.

Boosting hydrogen peroxide activation for the high-efficient removal of volatile dimethylsulfoxide over niobium-based catalysts

Dimethyl sulfoxide (DMSO) is an important solvent in numerous industries. The biodegrading process of DMSO is slow and produces toxic volatile compounds including CH3SCH3, CH3SH, and H2S. Hence, it is important to develop chemical methods for treating DMSO-containing wastewater. In the present work, niobium oxyhydroxide and niobium oxide were synthesized and used to activate hydrogen peroxide for the degradation of DMSO to DMSO2. The niobium oxyhydroxide catalyst exhibited much better catalytic activity for DMSO oxidation than niobium oxide. EPR spectra and radical scavenging experiments confirmed that O2•− and 1O2 are the main active species for the oxidation of DMSO. FTIR analysis and DFT calculation confirmed that the surface hydroxyl of niobium oxyhydroxide can be substituted by hydroperoxo group of H2O2 to form Nb−OOH group, which can directly oxidize DMSO or indirectly oxidize DMSO via O2•− and 1O2. However, H2O2 cannot form hydroperoxo group on the surface of niobium oxide, which might trigger the lower activity of niobium oxide catalysts than the niobium oxyhydroxide catalyst. The niobium oxyhydroxide catalyst exhibited good reusability and was promising for the treatment of DMSO-containing wastewater.

Effects of Synthesis Method on Catalytic Activities of Ag/TiO2 Catalyst in CO Oxidation Reaction

Supported silver catalysts on titanium dioxide have been synthesized by three different methods to compare catalytic activity in CO oxidation. The catalysts were prepared by the wet impregnation method with 10 mole% of silver. In the first method, the silver catalysts were impregnated on the titanium dioxide nanoparticles (Ag/TNP), while in the second method, the silver catalysts were impregnated on the titanium dioxide nanotubes (Ag/TNT). The third method, the silver catalysts were impregnated on the titanium dioxide nanoparticles before the nanotube process (Ag/TNP-TNT). The Ag/TNP and Ag/TNT catalysts showed highly dispersed silver nanoparticles with an average particle size of less than 5 nm on the surface of titanium dioxide, whereas the Ag/TNP-TNT catalyst exhibited much lower dispersion of silver nanoparticles. The highly dispersed silver on the titanium dioxide resulted in a large number of surface active sites (Ag0). The catalytic activity test found that the Ag/TNT catalysts with the highest number of active sites (2.20 × 1020 atom/g-catalyst) exhibited higher CO oxidation activity than the Ag/TNP and Ag/TNT catalysts with 100% CO conversion at 125°C.