Catalytic Activity For Oxidation Research Articles

Influence of atomic coordination on the activity of lattice oxygen and catalytic oxidation of toluene over regular Cu2O crystalline

VOCs oxidation over transition metal catalyst is commonly understood via the Mars-van Krevelen mechanism involving the crucial role of lattice oxygen (OL) activity, however, how it is influenced by atomic coordination is still unclear. Herein, we use model catalysts of Cu2O-cub, Cu2O-oct and Cu2O-dod with crystal planes of (100), (111) and (110), respectively, to investigate the OL activity and catalytic oxidation of toluene. The activity of Cu2O-oct is found to be the highest, followed by Cu2O-cub and Cu2O-dod. Experiments results combined with density functional theory show that, although low di-coordinated O atoms leads to the lowest surface oxygen vacancy formation energy (2.47eV) and the highest surface OL activity of Cu2O-cub, it cannot determine the activity. The lowest bulk oxygen vacancy formation energy (3.16eV) in Cu2O-oct terminated with tri-coordinated O atoms and open surface can accelerate the migration and replenishment of OL, thereby promoting the catalytic activity.

Uncovering the features of rhodium metabolism in China during 2011–2022

Rhodium has unique properties, such as high-temperature oxidation resistance and catalytic activity, making it irreplaceable in various domains such as automobile exhaust purification and chemical production. Given its pivotal role in facilitating China's green and low-carbon transition and the advancement of high-tech industries, rhodium has become a strategic resource. However, China heavily relies on importing rhodium to meet its domestic demand due to its limited rhodium reserve. This study employs dynamic material flow analysis (DMFA) to trace the rhodium flows throughout its entire life cycle in China for the period of 2011–2022 so that the key features of rhodium metabolism can be uncovered, including rhodium production, consumption, trade, in-use stock, and recycling. Our results show that the domestic demand for rhodium increased by 2.18 times during this study period. The cumulative rhodium consumption reached 82,890 kg, of which automobile three-way catalysts (TWCs) accounted for 71.85% of the total rhodium consumption, followed by the chemical sector (13.64%) and the glass sector (8.95%). China's accumulative imported rhodium reached 77,447 kg, meaning an import reliance rate (IRR) of 91.81%. The total recycled rhodium reached 21,184 kg, meaning a recycling rate (RR) of 58.63%. These findings reflect that China is facing several challenges in achieving sustainable rhodium resource management, such as a significant supply risk, and inadequate recycling. Consequently, China should establish a comprehensive rhodium recycling system and diversify its rhodium supply both domestically and internationally to ensure the sustainable supply of rhodium resources.

Synthesis, X-ray characterization of new copper-benzimidazole complex and investigation of its homogenous catalytic oxidation activity on selected primary and secondary alcohols

A new bis(benzimidazole)copper(II) complex, [Cu(Eap)2(CH3OH)](ClO4)2 was synthesized by the reaction between 2-(1-ethyl-2-(2-aminophenyl)-1H-benzimidazole (Eap) and copper(II)perchlorate hexahydrate (Cu(ClO)4·6H2O). Complex structure is mainly characterized by single crystal X-ray diffraction and other spectroscopic methods. Penta-coordinated copper(II) center surrounded with four nitrogen atoms of two identical benzimidaole ligands and an oxygen atom of methanol solvent. Designed complex is shown to be an active catalyst for the homogenous oxidation of selected primary and secondary alcohols. The effects of solvent, temperature, sub/cat ratio, time and substrate type on the catalytic reactions were investigated. The designed catalytic system showed good catalytic activity, and 100 % total product yields (aldehyde + acid) were achieved after 2 h.

Synthesis of a highly stable Mo-Fe bimetallic metal-organic framework and its catalytic activity for the selective oxidation of sulfides under mild conditions.

A novel Mo-Fe bimetallic metal-organic framework [Fe2(4,4'-bipy)Mo2O8]·2H2O (1) was synthesized and characterized by X-ray single crystal diffraction, infrared spectroscopy (IR), thermogravimetric analysis (TGA), ultraviolet-visible spectroscopy (UV-vis), and its magnetic properties were studied. The compound demonstrates insolubility in most solvents and exhibits significant chemical stability across a wide pH range. Typically, exceptional selectivity and efficient conversion of sulfides to sulfoxides using 1 with H2O2 have been verified under ambient conditions.

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.

Insights into the Synergistic Catalytic Effect of TiO2 Supported V-W Oxides for Selective C-H Bond Oxidation of Cyclohexane to KA Oil.

It is urgent to develop an efficient and stable non-noble metal catalyst for selective C-H bond oxidation of cyclohexane. Herein, a series of V-W oxides supported on TiO2 catalysts (V-W/TiO2) were fabricated. The V-W/TiO2 catalysts exhibited much higher catalytic activity for the selective oxidation of cyclohexane to KA oil, compared to that of V/TiO2 and W/TiO2 catalysts. The good distribution of active metals and the synergistic effect were responsible for the enhanced catalytic activity. H2-TPR results disclosed that the presence of V in V-W/TiO2 affected the reducibility of W6+ species, and XPS verified that an electronic interaction was formed between them. Such results led to good catalytic reusability of V-W/TiO2 catalyst during the reactions, and no obvious activity loss was found after six runs. The reaction mechanism was investigated, and the results verified that hydroxyl radicals generated from H2O2 homolysis were the main active oxidative species. Theoretical study revealed that V dopant could regulate electronic structure of adjacent O atom, facilitating the adsorption of cyclohexane, and lower energy was needed for the rate-limiting step over V-W/TiO2 during the whole oxidation reaction. This work developed an efficient V-W/TiO2 catalyst for the selective oxidation of cyclohexane via a synergistic effect.

Tailored electronic properties of PdAu nanocatalysts via one-step electrodeposition for high-performance glucose sensors

The development of efficient and reliable glucose sensors is crucial for the early detection and management of diabetes mellitus. This study introduces a novel one-step electrodeposition method for fabricating bimetallic palladium-gold (PdAu) nanocatalysts directly onto gold electrodes, aimed at enhancing the electrocatalytic performance for non-enzymatic glucose sensing. The one-step electrodeposition technique not only simplifies the fabrication process but also enables precise control over the morphology and electronic properties of the PdAu nanostructures. The optimized electronic interactions between palladium and gold within the nanocatalyst significantly enhance electron transfer kinetics, leading to a high electroactive surface area and improved catalytic activity for glucose oxidation. As a result, the PdAu electrodes demonstrated superior glucose sensing capabilities, with a low detection limit of 83 µM and an impressive sensitivity of 67.2 µA mM-1cm−2 across a linear range of 1–8 mM glucose. The catalyst also exhibited excellent selectivity against common interfering species, as well as remarkable stability and reproducibility over an extended period. These findings underscore the significance of the one-step electrodeposition method in producing bimetallic catalysts with tailored electronic properties, offering a promising approach for advancing electrochemical biosensors in diabetes diagnosis.

Ordered mesoporous CrCeOx catalyst prepared by hard template for toluene and formaldehyde combustion

The meso-Cr-Ce catalysts with different proportions of chromium and cerium were prepared using three-dimensional ordered mesoporous silica (KIT-6) as hard template by vacuum assisted impregnation method. The physicochemical properties of the catalysts were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), nitrogen adsorption-desorption (BET), transmission electron microscopy (TEM), Scanning electron microscopy (SEM) and temperature programmed reduction (TPR) techniques. The oxidation removal performance of toluene and formaldehyde was evaluated. The results show that all catalysts have better catalytic oxidation activity than the bulk counterpart. The meso-Cr-Ce-1 catalyst of same Cr/Ce molar ratio was larger in surface area (up to 186 m2/g) and could be reduced at lower temperatures, and exhibited the highest catalytic oxidation performance. At 30,000 h−1 of space velocity and 1000 ppm of VOC, toluene and formaldehyde conversions reached 90 % at 240 and 160 °C, respectively, and the apparent activation energies were 64.1 and 37.2 kJ/mol. The excellent performance of the catalyst is associated with its well-developed mesoporous structure, high specific surface area, good low temperature reducibility and dispersion and synergistic effect of active components.

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.

Surface Reconstruction of Single-Twinned AgPdIr Nanoalloy during the Formate Oxidation and Dehydrogenation Reactions.

Formate has emerged as a promising energy carrier to generate electrons via formate oxidation reaction (FOR) and hydrogen via formate dehydrogenation reaction (FDR), and it is desirable but difficult to design a novel bifunctional (electro)catalyst to improve reaction kinetics. Herein, we construct the single-twinned AgPdIr (t-AgPdIr) nanoalloy to improve the catalytic activity and stability for the formate oxidation and dehydrogenation processes. The t-AgPdIr nanoalloy, characterized by a distinctive twinned structure with strains and a downshift of the d-band center, demonstrates an improved peak current density of 4.6 A·mgPd -1, a diminished onset potential of 0.45 V, a superior activity retention of 55.7% after 600 cycles, and a current density of 0.73 A·mgPd -1 following potentiostatic polarization for 3600 s. Additionally, the t-AgPdIr catalyst shows an enhanced turnover frequency value of 407.3 h-1, a higher volume of generated H2 gas up to 51.8 mL after 120 min of reaction, and an activity recovery of 90.7% after five reaction cycles. Impressively, compared with the as-prepared nanoalloy, the postreaction catalyst shows a stable strain state along the twin boundaries and a surface segregation of Pd and Ir elements after the formate oxidation and dehydrogenation reactions.

Photothermal catalytic oxidation performance of cerium-based perovskite catalyst CeBO3 under full-spectrum: Effect of B-site elements

In this paper, a series of cerium-based perovskite catalysts were prepared by sol-gel method combined with high-temperature calcination method, and Mn, Cr and Ni were selected as B-site elements, respectively, and characterized as well as tested for the catalytic activity of toluene oxidation. The CeMnO3 catalyst has the smallest grain size (4.33 nm), the largest specific surface area (39.65 m2/g) and the largest Oads/Olatt ratio (0.65). Based on its good low-temperature reduction performance, abundant adsorbed oxygen content, higher light absorption capacity and other characteristics, CeMnO3 exhibits outstanding photothermal catalytic oxidation of toluene under full-spectrum condition of 550 mW/cm2, and its photothermal catalytic T90% is only 233 °C. The photothermal catalytic oxidation reaction of CeMnO3 follows the Mars-van Krevelen mechanism. The introduction of light in thermal catalysis produces photothermal synergy, which has a better effect than single thermal catalysis and has a positive effect on the degradation of toluene.

Acid washing-assisted synthesis of porous Co3O4 nanosheet catalyst featuring efficient benzene oxidation performance

Co-based catalysts exhibit considerable catalytic activity in oxidative reactions, yet challenges remain in synthesizing Co3O4 materials featuring both large surface area and high activity. Here, ultrathin La0.029CoOx nanosheets were post-treated with various concentrations of dilute nitric acid to obtain the two-dimensionally geometric Co3O4-H nanosheets catalysts. Among them, the resultant Co3O4-0.1H catalyst disclosed significantly enhanced catalytic activity, enabling to achieve 100 % conversion of benzene at 230 °C under an ultrahigh weight hourly space velocity (WHSV) of 60,000 mL·g−1·h−1. Additionally, the catalyst also displayed excellent catalytic durability and well catalytic stability over 5 cyclic tests and 45 h of long-period operation. A thorough characterization results revealed that the superior catalytic performance of Co3O4-0.1H was attributed to its distinct nanosheet morphology, high specific surface area and abundant surface defect sites. This work highlights the effectiveness and simplicity of acid washing treatment strategy in improving the catalytic oxidation activity of transition metal oxide catalysts.

Revealing the essence of anion ligands in regulating amorphous MnOx to activate peracetic acid for micropollutant removal

How the anion ligands of manganese precursors affect the catalytic activity of amorphous manganese oxides (MnOx) in Fenton-like process is poorly understood. Here, five amorphous MnOx synthesized by Mn(II) precursors with different ligands were characterized and adopted to activate peracetic acid (PAA) for bisphenol A (BPA) degradation. Although > 90 % BPA removal was achieved in the five MnOx/PAA processes via both adsorption and oxidation, the oxidation kobs greatly differentiates by the ligands types with the order of MnOx-N > MnOx-S > MnOx-Cl > MnOx-AA > MnOx-OA. Ligands types would affect the specific surface area of MnOx and their ability to adsorb BPA, however which is not the decisive factor in determining the contaminant oxidation efficiency. Multiple experimental results indicate that the generation of oxygen vacancies induced by the ligands alters the Mn(III)/Mn(IV) ratio, ultimately contributing to the different efficiency of BPA oxidation driven by the direct electron transfer mechanism. Moreover, amorphous MnOx holds the promise of practical applications in catalytic PAA of various micropollutants with good stability. This study advances the fundamental understanding of ligand-regulated amorphous MnOx-catalyzed PAA process.

Simultaneous Catalytic Oxidation of Benzene and Toluene over Pd-CeZrOx Catalysts

Since actual industrial emissions contain a wide range of volatile organic compounds, studies into the simultaneous catalytic degradation of multi-component VOCs are essential. This work developed Pd-CeZrOx samples for the simultaneous elimination of benzene and toluene. Firstly, CeZrOx supports were synthesized using several methods (co-precipitation, CTAB template co-precipitation, and sol–gel method). Pd active species were then added into the 1.0Pd-CeZrOx samples using the impregnation procedure. XRD, BET, NH3-TPD, Raman, EPR, XPS, and H2-TPR were utilized to analyze the as-prepared Pd-CeZrOx samples. The catalytic performance tests reveal that the performance of 1.0Pd-CeZrOx-CTAB outperforms that of 1.0Pd-CeZrOx-PM and 1.0Pd-CeZrOx-CASG, and 1.0Pd-CeZrOx-CTAB displays superior catalytic activity for both benzene and toluene oxidation. The improved redox properties, the abundant surface oxygen vacancies, and the surface Pd2+ species of the 1.0Pd-CeZrOx-CTAB sample may be responsible for the simultaneous degradation activity of benzene and toluene.

Selective Oxidation of p-Cymene over Mesoporous LaCoO3 by Introducing Oxygen Vacancies.

The liquid-phase catalytic oxidation of p-cymene to 4-methylacetophenone is an industrially significant reaction. However, the targeted oxidation of a specific C-H bond of p-cymene is extremely difficult due to there being many branched chains in p-cymene. In here, we designed a simple method to synthesize mesoporous LaCoO3 catalysts with rich oxygen vacancy (Oov) sites. The as-prepared mesoporous LaCoO3 after 550 °C calcination (mLaCoO3) exhibits remarkable catalytic activity for solvent-free oxidation of the p-cymene reaction, with a selectivity of over 80.1% selectivity for 4-methylacetophenone and a conversion of 50.2% for p-cymene (120 °C, 3 MPa). Besides, recycling studies have demonstrated that the mLaCoO3 catalysts can be reused ten times in the aerobic oxidation of the p-cymene reaction without significant catalytic activity reduce. The experimental and characterization results indicated that the mesoporous structure of the catalyst is conducive to the generation of surface Oov, which can properly facilitate ion spread during the catalytic process and afford enough O2 for intermediate species, thus is beneficial for the generation of 4-methylacetophenone. This work demonstrates that the selectivity oxide p-cymene with an O2 employing mLaCoO3 catalyst is highly promising for chemical industrial applications.

Machine Learning Accelerated Discovery of Entropy-Stabilized Oxide Catalysts for Catalytic Oxidation.

The catalytic properties of unary to ternary metal oxides were already well experimentally explored, and the left space seems like only high entropy metal oxides (HEOs, element types ≥5). However, the countless element compositions make the trial-and-error method of discovering HEO catalysts impossible. Herein, based on the study of the crystal phase and catalytic performance of the ACr2Ox catalyst system, the strong correlation between the single spinel phase and good catalytic activity of CH4 oxidation was inferred owing to the similar element importance sequences, which were acquired by the corresponding high accuracy machine learning models (cross-validation score >0.7). Furthermore, searching for negative data and choosing the proper training data resulted in high-quality regression models to search for better catalysts. Finally, the screened irregular catalyst Ni0.04Co0.48Zn0.36V0.12Cr2Ox with outstanding sulfur and moisture resistance and long-term stability (>7000 h, T90 = 345 °C) envisions the potential of applying the machine learning method to discover HEOs for target processes.

Regulating oxygen vacancies to optimize the electronic structure and catalytic activity of tungsten oxides for hydrogen evolution reaction

The undesirable intrinsic activity of tungsten oxides derived from poor conductivity and adverse hydrogen absorption energy is insufficient for their practical application. Herein, the tungsten oxides with adjustable oxygen vacancies were synthesized by a facile pyrolysis of ammonium paratungstate hydrate in controllable atmospheres. The structural characterizations confirmed that oxygen vacancies and crystalline phases in tungsten oxides depend on the pyrolysis atmosphere. The electrochemical test indicated a strong dependence between catalytic activity and oxygen vacancies in tungsten oxides. Combining experimental results and density functional theory calculations verified that introducing oxygen vacancies into tungsten oxides effectively modulates the surface electronic structure. The enhanced electronic conductivity by reducing band gap accelerates the electron transfer from catalysts into the reactive species. The optimized hydrogen adsorption energy by electron migration from O into W promotes the activation of reactive species at W sites and the desorption from O sites, thereby accelerating the reaction kinetics.

Tuning the Active Oxygen Species of Two-Dimensional Borophene Oxide toward Advanced Metal-Free Catalysis.

Two-dimensional (2D) borophene materials are predicted to be ideal catalytic materials due to their structural analogy to graphene. However, the lack of chemical functionalization of borophene hinders its practical application in catalysis. Herein, we reported a massive production of freestanding few-layer 2D borophene oxide (BO) sheets with tunable active oxygen species by a moderate oxidation-assisted exfoliation method. State-of-the-art characterizations demonstrated the evolution of active oxygen species from surface B-O species at the initial stage to the intermediate BxOy (1.5 < x/y < 3) species and eventually to bulk B2O3 with an increasing oxidation duration. As a result, the 2D BO sheet with enhanced B-O species exhibited a strikingly high catalytic activity for the aerobic oxidation of benzylamine into N-benzylidenebenzylamine. The formation rate of imine reaches as high as 29.7 mmol gcatal-1 h-1 under mild reaction conditions, higher than that of pristine borophene, boron oxides, graphene oxide, and other metal/metal-free catalysts in the reported literature. Density functional theory calculations further revealed the critical role of surface B-O species, which favor the adsorption and N-H activation of benzylamine for high activity and suppress the deep dehydrogenation, yielding an outstanding imine selectivity (>90%). This work paves the route for a moderate and scalable synthesis of few-layer BO sheets with highly active B-O species toward advanced metal-free catalysis beyond graphene.

Heteronuclear coordination polymers with imidazole ligand: Synthesis, characterization and alcohol oxidation activities

Two new heteronuclear Cd(II)/Pd(II) coordination polymers, [Cd2(µ-im)2(Him)4Pd(µ-CN)4]n (1) and [Cd(Him)2Pd(µ-CN)4]n (2) (Him: imidazole), have been synthesized under different conditions and characterized using elemental analysis, thermal analysis, FT-IR and Raman spectroscopy, single-crystal and powder X-ray diffraction techniques. In 1, the Cd(II) ions are bridged by imidazolate ligands to generate 1D chain structure. Neighbouring 1D chains were linked by [Pd(CN)4]2- ions to form 3D framework. In 2, the metal ions are bridged by cyanide ligands to generate 2D [Cd2Pd2(µ-CN)4]n network. Catalytic peroxidative oxidation activity of 1 and 2 was examined on the oxidation of benzyl alcohol using tertiary-butyl hydroperoxide (t-BuOOH) as the oxygen source. The compound 1 exhibited over 90 % product conversion at 80 °C in 24-hour reaction time. In addition, the catalyst exhibited high selectivity towards benzaldehyde and no over-oxidation product (benzoic acid) was detected.

A combination of covalent and noncovalent restricted‐intramolecular‐rotation strategy for supramolecular AIE‐type photosensitizer toward photodynamic therapy

AbstractPhotodynamic therapy (PDT) is a promising noninvasive method for targeted cancer cell destruction. Still, its effectiveness is often hindered by the aggregation‐caused quenching effect of organic photosensitizer (PS) in aqueous environments. Here, we have employed a combination of covalent and noncovalent restricted‐intramolecular‐rotation strategies to develop supramolecular PSs with aggregation‐induced emission (AIE) characteristics. Firstly, a water‐soluble octacationic molecular cage (1) with a bilayer tetraphenylethene (TPE) structure has been designed and synthesized, which minimizes intramolecular rotation of TPE moieties and achieves the single‐molecule‐level aggregation by the covalent restriction of intramolecular rotation (RIR) via molecular engineering synthesis. Compared with its single‐layer TPE analog, 1 exhibits superior efficiency in generating reactive oxygen species (ROS) including superoxide radical (O2−•) and singlet oxygen (1O2) upon white‐light irradiation. Subsequently, by forming a 1:4 host–guest complex (1@CB[8]4) between 1 and cucurbit[8]uril (CB[8]), O2−• generation can be further enhanced by the noncovalent RIR via the host–guest assembly. Additionally, 1@CB[8]4 as a photocatalyst promotes rapid oxidation of nicotinamide adenine dinucleotide (NADH) in water. Given its Type‐I ROS generation and catalytic activity for NADH oxidation, 1@CB[8]4 acts as a supramolecular AIE‐type PS to exhibit strong photo‐induced cytotoxicity upon white‐light irradiation under hypoxic conditions, showcasing its potential for synergistic PDT.