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Selective catalytic reduction (SCR) catalysts is used widely to reduce NOx emissions from diesel engines. However, improvements in de-NOx performance are required to meet future standards of near-zero NOx emissions. This study examines the effectiveness of dual-point NH3 injection technology, in which gaseous NH3 is injected into both closed coupled and under floor SCR catalysts. The NOx removal efficiency of dual-point NH3 injection is compared with that of single-point injection in a World Harmonized Transient Cycle test. The results show that dual-point injection of NH3 gas can effectively reduce NOx emissions from diesel engines due to superior temporal and spatial distribution of NH3 gas in an SCR catalyst. [ABSTRACT FROM AUTHOR]

Ce-based catalysts have been widely used in the removal of nitrogen oxides from industrial flue gas because of their good catalytic performance and environmental friendliness. However, the mechanism of alkali metal poisoning in Ce-based catalysts remains to be further studied. This work involves the preparation of the K/Na-poisoned CeWTi catalyst via the impregnation method for assessing its performance in NO removal. Experiments show that both K and Na exhibit detrimental effects on the CeWTi catalyst, and the loading of alkali metal reduces the specific surface area and pore volume of the catalyst. Furthermore, the presence of alkaline metals results in a notable decline in the CeWTi acid concentration, particularly in Lewis acid sites. Concurrently, the levels of Ce3+, oxygen vacancies, and reducing agents on the catalyst surface decrease, leading to diminished reduction capability and eventual catalyst deactivation. The application of a BP neural network for catalyst activity prediction yielded an average relative error of approximately 0.73%, indicating enhanced accuracy in prediction outcomes. This work explored the cause of alkali metal poisoning of the CeWTi catalyst and provided an effective prediction method for the lifetime of CeWTi catalyst, which provided theoretical guidance for the engineering application of Ce-based catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • NO x conversion and N 2 selectivity are significantly enhanced in the presence of SO 2. • The decrease in CO oxidation ability is the main reason for the improvement in NO reduction performance. • L-H reaction pathways for CO oxidation are inhibited by the formation of sulfate species. • The promotional mechanism of SO 2 on CO-SCR reaction over Ir-based catalysts is proposed. Generally, sulfur poisoning is considered to be one of the main factors contributing to the deactivation of selective catalytic reduction of NO x by CO (CO-SCR) catalysts, while the promotional effect of SO 2 on NO reduction over Ir/SiO 2 is observed which is an interesting scientific phenomenon. After the introduction of 20 ppm SO 2 , NO x conversion increased from ∼ 40 % to ∼ 90 % at 275 °C, and N 2 selectivity increased from ∼ 80 % to 100 % at 200 ∼ 300 °C. Furthermore, the promoting effect could remain unchanged after 24 h of continuous reaction. However, the temperature point for achieving complete conversion of CO increased from 225 °C to 275 °C after the introduction of SO 2. Experimental characterization and theoretical calculation jointly proved that the inhibition of CO oxidation by the generation of sulfate was the main reason for promoting NO reduction. Under the coexistence of O 2 and SO 2 , SO 2 was firstly oxidized to SO 3 on the iridium surface and generated sulfate species on surface hydroxyl groups of SiO 2. Some active sites for O 2 adsorption were covered by the generated surface sulfate, and adsorbed CO was hard to react with adsorbed O 2 , resulting in Langmuir–Hinshelwood (L-H) reaction pathways for CO oxidation being inhibited. Therefore, unoxidized CO reacted with NO adsorbed species and generated N 2 O to generate N 2 and CO 2 , improving NO reduction. This new insight has implications for understanding the promotional effect of SO 2 on NO reduction with CO in the presence of O 2. [ABSTRACT FROM AUTHOR]

Heavy metal ion pollution poses a serious threat to the natural environment and human health. Photoreduction through Bi-based photocatalysts is regarded as an advanced green technology for solving environmental problems. However, their photocatalytic activity is limited by the rapid recombination of photogenerated e− and h+ pairs and a low photo-quantum efficiency. In this work, an optimal precursor of Bi-based MOFs was identified by using different solvents, and rod-like Bi2O3 materials were derived by in situ oxidation of Bi atoms in the precursor. The adsorption and photocatalytic reduction efficiency of the prepared Bi2O3 materials for Cr(VI) were evaluated under visible light irradiation. The results showed that the prepared materials had a large specific surface area and enhanced visible light absorption. Bi2O3(DMF/MeOH-3)-400 had a large specific surface area and many active adsorption sites, and it had the highest adsorption of Cr(VI) (49.13%) among the materials. Bi2O3(DMF/MeOH-3)-400 also had the highest photocatalytic reduction efficiency, and it achieved 100% removal of 10 mg·L−1 Cr(VI) within 90 min under light. In addition, the material showed remarkable stability after three consecutive photocatalytic cycles. The enhanced photocatalytic performance was mainly attributed to the fast separation of electron–hole pairs and efficient electron transfer in the MOF-derived materials, which was confirmed by electrochemical tests and PL spectroscopy. Reactive species trapping experiments confirmed that electrons were the main active substances; accordingly, a possible photocatalytic mechanism was proposed. In conclusion, this work provides a new perspective for designing novel photocatalysts that can facilitate the removal of Cr(VI) from water. [ABSTRACT FROM AUTHOR]

A simple electrochemical sensor was developed towards the widely used insecticide Imidacloprid (IMI) using a redox active polymer, poly(1,5-diaminoanthraquinone) (PDAAQ) modified glassy carbon electrode (GCE). The electro catalytic reduction of IMI was obtained using the GCE/PDAAQ electrode in phosphate buffer solution having pH 7. The irreversible reduction of IMI occurs at a potential of −1.031 V with a slight shift towards negative potential with increase in concentration of IMI. The linear range obtained is 9.98 × 10–6 to 6.6 × 10–4 M with a limit of detection 2.95 × 10–7 M. Repeatability and reproducibility of the sensor was checked and was found to be in the acceptable range with relative standard deviation less than 5%. Selectivity of the sensor was studied in presence of various metal ions and organic molecules and found that there is no significant interference. IMI analysis was done using spike recovery tests in well water and cucumber juice samples which shows that the developed sensor can be successfully applied to the trace determination of IMI in real samples. [ABSTRACT FROM AUTHOR]

Hexavalent chromium (Cr(VI)) has attracted great considerations due to their high toxicity, teratogenicity, and carcinogenicity. In this study, four Zr‐MOFs were synthesized and used to comparative study their catalytic performances of oxalic acid (OA) for Cr(VI) removal. Results showed that the removal efficiency for Cr(VI) was reached 65.91%, 78.64%, 53.58%, and 96.32% by MOF‐525, MOF‐525(Co), MOF‐525(Zn), and MOF‐525(Fe) in the presence of OA when the initial Cr(VI) concentration was 100 mg·L−1, respectively. The single‐factor experiments for further improving the Cr(VI) removal by MOF‐525(Fe)/OA demonstrated that the optimal conditions were OA dosage of 790 mg·L−1, and MOF‐525(Fe) dosage of 500 mg·L−1 and pH of 2.0, and the MOF‐525(Fe)/OA system could be used to treat Cr(VI)‐containing wastewater at concentrations below 50 mg·L−1. Ionic strength studies indicated that Na+, K+, Mg2+, Cl−, and SO42− had little effect on the catalytic reduction of Cr(VI), while high concentrations of Ca2+ (0.10 and 0.25 mol·L−1), NO3− (0.25 mol·L−1), and PO43− (0.25 mol·L−1) had significant inhibition effects. The reusability experiments showed that the stability of MOF‐525(Fe) was excellent, and it could be used for potential applications. Based on the results of Fourier transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), and Electron Paramagnetic Resonance spectrometer (EPR), the possible reduction mechanism of Cr(VI) by MOF‐525(Fe)/OA system was proposed as follows: The complexation of OA with Fe3+ was first complexed to produce Fe2+ and CO2•−, then Cr(VI) was combined with Zr–O and Fe–O clusters in MOF‐525(Fe) to obtain activation energy, and the reduction ability was enhanced at the same time; finally, Cr(VI) obtained electrons from CO2•− and was sequentially reduced as Cr(V) and Cr(III). [ABSTRACT FROM AUTHOR]

Over the past few years, heterogeneous catalysis has been recognized as a versatile and efficient approach for applications in environmental remediation systems. The water treatment field is one of the most prominent beneficiaries of these various catalytic processes due to the crucial need to promote water reuse. However, there are still shortcomings related to the efficiency of these processes when applied to increasingly complex water matrices composed of different classes of contaminants. The present review aims to address the advantages associated with the application of catalytic processes and the diverse catalysts for water treatment while exploring how to take advantage of process integration as a solution to address the challenges posed by the growing complexity of environmental matrices. [ABSTRACT FROM AUTHOR]

The development of Cu‐SSZ‐13 represents a significant breakthrough in the field of NOx removal from mobile exhaust, demonstrating excellent selective catalytic reduction (SCR) activity across a broad temperature range (200–500°C). However, the limited reactivity of Cu‐SSZ‐13 at temperatures below 200°C poses a challenge for the removal of NOx emitted during vehicle cold starts. To stimulate new efforts to enhance low‐temperature SCR performance, this review provides a fundamental understanding of the nature of Cu‐SSZ‐13 in catalyzing the SCR reaction. The structures, coordination environments, and oxidation states of Cu2+ during the SCR reaction, as well as the redox cycle pathway of Cu2+ ions and the characteristics of the rate‐determining step, were discussed. Based on these insights, several strategies for improving the low‐temperature activity of Cu‐SSZ‐13 are proposed. Finally, the review offers a perspective on the future of low‐temperature SCR of NOx over Cu‐SSZ‐13. [ABSTRACT FROM AUTHOR]

The tin-containing Lewis acid group (C2F5)3Sn was combined with a phosphonium ylide as base function in one molecule: o-[(C2F5)3Sn]-C6H4(Ph)2PCMe2. It was prepared by reacting the ortho-lithiated triphenylphosphoniumdimethylmethylide (o-Li-C6H4)(Ph)2PCMe2 with the stannyl chloride (C2F5)3SnCl to afford o-[(C2F5)3Sn]-C6H4(Ph)2PCMe2 in 86 % yield. It forms a ring structure with a bond between tin and the ylidic carbon atom both in solution and in the solid state and can thus be considered as a hidden frustrated Lewis pair. The title compound is unreactive towards H2, CO2, CS2, PhNCO and decomposes in the presence of SO2 or NH3. However, it is active in the catalytic reduction of CO2 with pinacolborane, H–BPin. The title compound reacts slowly with H–BPin in an unselective reaction from which a reduction product with cleaved C2F5 group, the phosphonium stannate (II) o-[(C2F5)2Sn]-C6H4(Ph)2PCHMe2, could be obtained in small amounts. [ABSTRACT FROM AUTHOR]

This paper studies the catalytic hydrogenation reduction of lignin-derived phenolic compounds, such as catechol, guaiacol (O-methoxyphenol), phenol, P-methylphenol, O-ethylphenol, O-ethoxyphenol, etc. The reaction system focuses on the catalytic performance of hydrodeoxygenation reactions involving the phenolic derivatives of the lignin depolymerization products catechol and guaiacol. A series of Al2O3-TiO2 composite oxide supports with different Al/Ti ratios were prepared by a co-precipitation method, and a 5% Pd/Al2O3-TiO2 bifunctional catalyst was prepared by an impregnation method and characterized with XRD, SEM, BET, NH3-TPD, etc. Among these, the Pd/Al2Ti1 catalyst had the most excellent catalytic performance. At 100 °C and 2 MPa hydrogen pressure, the conversion of catechol was as high as 100%, and at 100 °C and 5 MPa hydrogen pressure, the conversion of guaiacol reached 90%. [ABSTRACT FROM AUTHOR]

Water contamination by toxic organic dyes represents a significant global challenge necessitating effective remediation strategies. Due to their high catalytic activity, considerable attention has been gained to metal-based nanocatalysts. Cellulose acetate sheets supported by gold nanoparticles through a reduction method were synthesized. The composite synthesized material presents a compelling platform for catalytic reduction in the remediation of toxic organic pollutants, ensuring controlled particle size and stability. In this study, the prepared cellulose acetate sheet (CAsheet) was dipped in a 0.001 M aqueous chloroauric acid (HAuCl4) solution and reduced by immersion in a 0.1 M sodium borohydride (NaBH4) aqueous solution. After the successful preparation of virgin cellulose acetate sheet (CAsheet) and gold-supported cellulose acetate sheet (Au-CAsheet) samples were assessed by scanning electron microscopy (SEM), X-ray crystallography (XRD), energy dispersive X-rays spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR) analysis. The catalytic reduction reaction of toxic compounds i.e. reduction of 4-nitroaniline (4-NA), Congo red (CR), and reactive yellow (RY-42) by using NaBH4. The catalytic activity of the Au-CAsheet was exhibited by the reaction rate constant (kapp) values 0.3189, 0.1596, and 0.1593 min−1 for CR, 4-NA, and RY-42 respectively. This kind of procedure for Au-CAsheet synthesis may be valid for different applications in catalysis, sensing, and environmental application. [ABSTRACT FROM AUTHOR]

In this study, we investigate the electrochemical properties of a novel copper complex (CuL2) derived from the Schiff base ligand N-3-bromopropylsalicylaldimine (LH). We also examine its interaction with chicken blood double-stranded DNA (cb-ds DNA) in phosphate buffer solution (PB) at physiological pH 7.2 using cyclic voltammetry (CV) techniques. The interaction mechanism of nitrite with CuL2, involving the CuII/CuI redox system, is explored. The CuL2 complex was electropolymerized on glassy carbon (GC) and fluorine tin oxide (FTO). The morphology of PolyCuL2 formed on FTO was analyzed using scanning electron microscopy (SEM) and its elemental composition determined by EDX analysis. The modified electrode polyCuL2/GC exhibited efficient catalytic activity for the electroreduction of oxygen (O2) in homogeneous electrocatalytic media. The binding constant (Kb) of the DNA-CuL2 adduct, determined from CV measurements, was found to be 1.33×105, closely matching the value obtained from molecular docking studies (1.75×105). Docking studies indicate that the CuL2 complex binds to DNA in the minor groove binding mode. The anodic peak potential shift in the negative direction suggests an electrostatic interaction between CuL2 and DNA. [ABSTRACT FROM AUTHOR]

Hazardous inert pollutants, organic dyes, pharmaceuticals, and widespread discharge of pesticide contaminants into water sources due to population growth and global industrialization are becoming some of the world's most pressing health problems. A novel kind of carbonitride or transition metal carbide, known as two‐dimensional (2D) MXene materials, has shown promise in adsorbing several heavy pollutants, including lead, mercury, chromium, and copper. The removal of pollutants from watery environments using MXene nanocomposites is reviewed in this article. This review highlights the different synthesis methods and potential of MXene nanocomposites to improve water purification methods by offering a thorough overview of recent developments in their application for photocatalytic wastewater treatment. This review further explores existing constraints, looks at the mechanisms behind MXene‐mediated pollutant degradation, and suggests future research approaches to improve MXene nanomaterials for extensive ecological and wastewater treatment applications. [ABSTRACT FROM AUTHOR]

Copyright of Mining & Metallurgical Engineering is the property of Mining & Metallurgical Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

V/S co‐doped SnO2 bimetal sulfur‐oxides catalysts labeled as (Sn,V)1‐x(S,O)2‐y or (SnVSO) with heterovalent state and oxygen vacancy defect are prepared via a green and facile method. The presence of SnVSO in the heterovalent states of Sn4+/Sn2+ and V5+/V4+ facilitates the rapid transfer of the electrons. It improves the electronic charge lifetime, accelerating the efficiency of the catalytic reduction of pollutants. The V/S co‐doped SnO2 regulates the bandgap energy structure. The hydrazine adjusts the heterovalent metal states to reduce Sn4+ to Sn2+ and V5+ to V4+. Also, it introduces oxygen vacancies to SnVSO to maintain the charge equilibrium and increase the active surface reactive sites, which enhance the catalytic activity. The SnVSO‐3 prepared with 0.4 mL hydrazine exhibits excellent catalytic activity, which wholly reduces 20 ppm of 100 mL methyl orange (MO), rhodamine B (RhB), methylene blue (MB), hexavalent chromium (Cr6+), and 4‐nitrophenol (4‐NP) within 6 min. In addition, the SnVSO‐3 also has good stability after repeated 6 runs with a reduction efficiency of 96.8%. Therefore, the V/S co‐doped SnO2 sulfur oxide catalysts have a promising potential for reducing Cr6+ and organic pollutants. [ABSTRACT FROM AUTHOR]

Organic pollutants negatively impact the environment, including air, water, soil, and living organisms. These pollutants come from various sources, including industrial, agricultural, and domestic activities. Removing organic pollutants from the environment is a difficult task and requires a combination of prevention and innovative strategies. Herein a novel nanocomposite consisting of beta‐cyclodextrin (β‐CD) modified silver (Ag@β‐CD) and gold (Au@‐β‐CD) nanoparticles (NPs) attached on the surface of Fe3O4@TiO2 core–shell structure with an average 530 nm diameter in an eco‐friendly environment is presented. In the first step, Au@‐β‐CD and Ag@‐β‐CD are synthesized, and the core–shell structure is modified by these nanoparticles. The catalytic activities of the synthesized nanocomposite are investigated for the reduction of RhB and 4‐NP and the photodegradation of MB. The synthesized composite shows the highest catalytic performance in the reduction of RhB and 4‐NP and photodegradation of MB, and the reactions are completed in 75, 45 s, and 16 min with a rate constant (k) 0.03 ± 0.005 s−1, 0.07 ± 0.01 s−1, and 0.25 ± 0.07 min−1, respectively. The reduction and photodegradation reactions follow the first‐order rate law. The catalyst is reused for six cycles after separation from the reaction system by an external magnetic field. [ABSTRACT FROM AUTHOR]

The applicability of some commercial catalysts in the conversion of carbon dioxide into syngas is estimated. Catalysts based on Cu and transitional metals (Fe, Ni, Co) and used in large-capacity hydrogenation and syngas technology are selected for study. They include NIAP-03-01 (steam conversion of hydrocarbon gases), NIAP-06-06 (low-temperature CO conversion), AmoMax 10 (synthesis of ammonia), and Со-Al2O3/SiO2 (synthesis of hydrocarbons). The catalysts are tested in the reduction of СО2 using the reverse water gas shift (RWGS) reaction. Cu-containing catalyst NIAP-06-06 is shown to have the highest activity and selectivity in the reduction of СО2, with 97% equilibrium in the RWGS reaction being reached at GHSV = 32 000 h−1, Н2/СО2 = 2, and temperatures of 500–800°C. The possibility is shown of obtaining syngas with the composition required for the synthesis of hydrocarbons and methanol by changing the parameters of СО2 reduction (temperature, Н2/СО2 ratio). [ABSTRACT FROM AUTHOR]

Urea-based selective catalytic reduction (SCR) is highly efficient for NOx abatement within a diesel aftertreatment system. However, abnormally high NOx emissions in the aftertreatment system tailpipe during WHSC (World Harmonized Steady-State Cycle) evaluation have been observed due to insufficient urea decomposition or mixing, which cannot be predicted by the current uniform 1D (one-dimensional) modelling approach with different urea dosing ratios. As a result, a multi-channel model has been developed to investigate the effect of urea maldistribution on aftertreatment system performance, where the uniformity index (UI) is used as a characteristic parameter to describe urea mixing efficiency. It was found that NOx emissions at the tailpipe can be successfully described with the multi-channel model even with a relatively high UI (UI = 0.95). Additionally, an improved segment UI factor as a function of mass flow rate has also been applied for maldistribution description, wherein better correlation with the measured NOx emission can be obtained. [ABSTRACT FROM AUTHOR]

After the implementation of ultra-low emission policies, the pollutant emissions from the coal-fired power generation systems in China have been further reduced, which creates more critical requirements for the control accuracies of denitrification systems using selective catalytic reduction technology and controls of ammonia slip. This article presents big data-based technologies for controlling ammonia slip, through precise ammonia injections, which were applied and demonstrated for a flue gas denitrification system of a Chinese coal-fired power plant. Through examinations and analyses of the basic operating conditions of the unit and parameters, such as NOx emission control efficiency, ammonia injection amount of the denitrification system, and non-uniformity of NOx concentrations in the denitrification zone were compared before and after the implementation of these technologies, the outcome proves that this artificial intelligence algorithm based on big data can effectively solve the automatic control problem of denitrification system under complex working conditions such as varied unit loads, day and night operation changed coal source. In addition to the effective controls of the ammonia slip of the system, the controls of NOx emission of the system become more stabilized, creating a successful example for wider applications of these precise ammonia injection control technologies in the future. Analyses show that NOx non-uniformities can be reduced by more than 50% under both stable and variable load conditions. NOx fluctuations at the unit outlet are tightly controlled within ±10 mg/Nm3 under variable load conditions and within ±5 mg/Nm3 under stable conditions. The average ammonia injection amounts under various load conditions have decreased by 15.7%. [ABSTRACT FROM AUTHOR]

Copyright of Precious Metals / Guijinshu is the property of Precious Metals Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The thermal decomposition of a heat-not-burn (HNB) tobacco at four temperatures (250–400 °C) was studied via thermogravimetric analysis (TGA) and Multi-shot pyrolizer experiments (Py-GC/MS), and the effect of four potential additives, USY Beta and beta zeolites and Silica Lovel 6000 and SBA-15 silicates at three concentrations (5, 15 and 25% w/w) under an inert and oxidative atmosphere was analyzed. Different techniques were applied showing that the presence of the additives modifies the decomposition processes (TGA). Py-GC/MS showed that these tobaccos generate large amounts of Nicotine and Glycerine. Acid compounds are the most abundant compounds under an inert atmosphere, while Oxygenated compounds predominate under an oxidative atmosphere. In both atmospheres, Furans and Aromatics present in a significant abundance at high temperatures. The additives used reduce both the number and the concentration of most of the compounds generated, especially at high temperatures and concentrations. Moreover, SBA-15 shows good aptitudes to reduce the formation of some individual compounds included in the FDA's HPHC list, such as Acetone and Acetaldehyde. Finally, smoking experiments corroborated that all additives produce marked reductions in TPM, i.e., the majority fraction obtained, and in practically all the compounds generated. Phenol, a toxicant compound that was detected in a significant amount, is also markedly reduced. SBA-15 is the material that presents a major reduction in the TPM and the principal compounds generated. These results may be of great interest for further reducing the toxicity of smoking this type of heat-not-burn tobacco product. [ABSTRACT FROM AUTHOR]

The structure of lignin was characterized with different industrial lignin as raw materials. The differences of phenolic monomers prepared by different lignin were studied by using oxidation and reduction catalytic degradation methods of basic nitrobenzene. The results showed that, 1) The contents of lignin were significantly different, in which organic acid lignin A sample had the highest lignin content (96.5 wt%), but that in the organic acid lignin B (48.7 wt%) was the opposite. 2) The structural destruction degree of lignin was inconsistent, the signal peak of β-O-4 (A) structure was detected in alkali lignin and organic acid lignin A samples, while no signal peak was observed in sodium lignosulfonate and organic acid lignin B samples. 3) There was little difference in the molecular weight of all lignin samples, distributed in 1 997-2 301 g/mol. 4) The yields of aromatic monomers derived from the reductive catalytic depolymerization of lignin were 47.5 mg/g (sodium lignosulfonate), 27.3 mg/g (alkali lignin), 49.3 mg/g (organic acid lignin A) and 26.9 mg/g (organic acid lignin B), respectively, which were superior to the results of alkaline nitrobenzene oxidation. It can be seen that the purity (lignin content) and structural features of lignin from different sources were different, thus resulting in lower aromatic monomer yields derived from the depolymerization of lignin than that of natural lignin. The results could provide an important theoretical basis for high value utilization of lignin [ABSTRACT FROM AUTHOR]

Although bimetallic noble nanostructures often possess high activity in nanocatalysis, their controllable fabrication, tunable catalytic activity, and easy separation remain significant challenges. In this study, an Fe3O4@AgPd/Polydopamine (Fe3O4@AgPd/PDA) nanosnowman loaded with an AgPd nanocage was designed by a one-step template-disposition-redox polymerization method. The AgPd nanocage endowed the product with high catalytic activity for the reduction of organic pollutants (4-NP, MO, MB). Interestingly, under near-infrared (NIR) light, the catalytic kinetics of the Fe3O4@AgPd/PDA nanosnowman on catalytic reduction of organic pollutants increased by 2.6, 1.57, and 5.45 times, respectively. The asymmetric nanostructure facilitated the separation of electron–hole pairs, promoted electron transfer, and accelerated the catalytic activity. Density functional theory (DFT) analysis indicated that the electron transfer between the AgPd alloy and the Fe3O4 nanosphere played a critical role on the high catalytic activity. Moreover, Fe3O4@AgPd/PDA also demonstrated excellent catalytic activity in the Heck carbon–carbon coupling reaction with a >95% conversion rate and >99% selectivity. Owing to the well-encapsulated PDA shell and outstanding magnetic properties, the Fe3O4@AgPd/PDA nanosnowman exhibited good cyclic catalytic activity. With its multi-mode catalysis, NIR-enhanced catalytic activity, and easy separation, the Fe3O4@AgPd/PDA nanosnowman exhibits great application potential in nanocatalysis. [ABSTRACT FROM AUTHOR]

In this study, 2D multimetallic MOFs combined with the advantages of 2D nanosheets, with the synergetic effect of multimetallic nodes, exhibited good photocatalytic activity for reduction of CO2. Herein, a 2D MOF‐Co/Cu/Fe were successfully prepared via one‐pot stirring of the solutions of multimetal salts and organic ligands at room temperature. Introduction of the second and third metal (Cu and Fe) into MOF‐Co does not change the 2D morphology of MOFs, although it improved the photocatalytic CO2 reduction performance by broadening the light absorption range of 2D MOF‐Co, accelerating the separation efficiency and transfer rate of photogenerated carriers. Upon irradiation with full‐spectrum light, the average CO yield of 2D MOF‐Co/Cu/Fe achieved 17.06 µmol·g−1·h−1, being about 1.8 and 1.2 times that of 2D MOF‐Co and 2D MOF‐Co/Cu. This work provides an insight into 2D multimetallic MOFs‐based photocatalysts in catalytic CO2 reduction. [ABSTRACT FROM AUTHOR]

Ni/Zn‐MOF composites with photoelectrocatalytic (PEC) performance for Cr(VI) reduction were prepared via hydrothermal method and calcinating method. The as‐prepared NiO/ZnO composites exhibited uniform morphology. When being subjected to an external voltage of 0.7 V and irradiated with visible light for 120 min, the NiO/ZnO composite exhibited a Cr (VI) reduction efficiency of almost 100 %, outperforming ZnO and NiO counterparts. The effects of the content of NiO to ZnO and different calcination temperatures on PEC performance were also investigated. Additionally, elimination experiments results indicated that photo‐generated electrons (e−) play a crucial role in the catalytic reduction of Cr(VI). The notable enhancement in the photoelectrocatalytic performance can be credited to the applied bias voltage and the formation of a p‐n heterojunction between NiO and ZnO. Consequently, the NiO/ZnO nanocomposites exhibit significant potential for the PEC reduction of Cr(VI). This capability underscores the promise of NiO/ZnO nanocomposites for applications in the photoelectrocatalytic reduction of Cr(VI) and related environmental remediation processes. [ABSTRACT FROM AUTHOR]

The rapid transfer and separation of photogenerated electrons is very important for the improvement of photocatalytic efficiency. Here, chiral induced spin selectivity effect (CISS effect) was developed to accelerate electron transfer for efficient photocatalytic hydrogen production. A chiral and achiral racemic supramolecular Pd(II) complex nanofiber was fabricated via supramolecular self‐assembly of chiral L−Py or its racemes with Pd(II) and used to modify carbon nitride (g‐C3N4). The obtained chiral photocatalyst L−Py−Pd/g‐C3N4‐4 and achiral photocatalyst Rac‐Pd/g‐C3N4‐4, show enhanced photocatalytic activities with hydrogen evolution rates of 2476 and 1339 μmol g−1 h−1, respectively, while that of pure g‐C3N4 is 30.5 μmol g−1 h−1. Chiral photocatalyst has 85 % higher activity than achiral one and is 82.5‐fold of pure g‐C3N4, due to better suppression of the recombination of photogenerated electron‐hole pairs in the interface of g‐C3N4 contact with chiral molecule. Spectral tests and photoelectrochemical tests proved that the chiral supramolecular Pd(II) complex can act both as an electron spin filter and hydrogen reduction catalytic center to enhance photocatalytic efficiency. This work offers a new route to facilitate electron transfer by the CISS effect for photocatalytic hydrogen evolution. [ABSTRACT FROM AUTHOR]

This article presents the first practical engine system using ammonia (NH 3) as a mono-fuel. To address the low flammability and distinctive odor, the system incorporates a four-cylinder spark ignition engine with an onboard reformer applying autothermal reforming to generate hydrogen as a combustion promoter, a three-way catalyst (TWC), and selective catalytic reduction (SCR) catalyst as an NH 3 adsorbent. The system successfully reduced nitrogen-based exhaust emissions during cold starts, which was a challenge, by controlling the air-fuel ratio (λ). Nitrogen oxides were suppressed by rich combustion until the TWC became active, while NH 3 passing through the TWC was adsorbed by the SCR catalyst. After TWC activation, simultaneous purification of NH 3 and nitrogen oxides was achieved by controlling λ at 1. The adsorbed NH 3 was subsequently purified along with nitrogen oxides via the SCR reaction by lean operation, regenerating the adsorption capacity and achieving near-zero emissions. • An NH 3 mono-fueled engine system with a reformer and an adsorbent was proposed. • Successful cold start-up was achieved with suppressed NH 3 , NO x , and N 2 O emissions. • Rich combustion reduced NO x and N 2 O until a three-way catalyst is activated. • Adsorbed NH 3 was purified with NO x by lean operation using SCR reactions. • Production of N 2 O on TWC was reduced avoiding lean and low temperature conditions. [ABSTRACT FROM AUTHOR]

To investigate the substrate recognition mechanism of trypsin-like protease cocoonase (CCN), mutational analyses were conducted at key substrate recognition sites, Asp187 and Ser188, and their effects on substrate specificity and enzymatic activity were evaluated. Mutants with the Asp187 substitution exhibited a significant reduction in catalytic activity compared with the wild-type enzyme, whereas the Ser188 mutants displayed a comparatively minor effect on activity. This indicates that Asp187 plays a crucial role in catalytic function, whereas Ser188 serves a complementary role in substrate recognition. Interestingly, the substitution of the Asp187 to Glu or Ser caused novel substrate specificities, resulting in the recognition of Orn and His residues. In addition, when Asp187 and Ser188 were substituted with acidic residues (Glu or Asp), both the precursor proCCN and mature CCN proteins retained highly similar secondary and tertiary structures. This reveals that the structural characteristics of precursor proteins are maintained in the mature proteins, potentially influencing substrate recognition and catalytic function. These findings suggest that the pro-regions of these mutants interact much more tightly with the mature enzyme than in the wild-type CCN. These results provide fruitful insights into the structural determinants governing substrate recognition in enzyme variants. [ABSTRACT FROM AUTHOR]

Heteroleptic magnesium hydrides are important for their stoichiometric and catalytic reduction chemistry. Their primary nucleophilic site is typically the hydride, while the ancillary ligands commonly used are mostly spectators. Chemically non-innocent ligands in comparison are rarely applied on MgH as their reactivity can be complex. Milstein et al. have recently reported Mg-mediated alkyne hydrogenation by using their metal–ligand cooperation (MLC) concept on a dearomatized picolyl-based PNP pincer that is non-innocent with a nucleophilic nature. A '(PNP)MgH' is noted as the active catalyst in hydrogenation but without structural validation. Inspired by the same, we report herein a novel NNN-chelator (MesL) with a dearomatized picolyl moiety and its well-defined MgH. Having two prominent nucleophilic sites, the present MgH shows metal–ligand competition while reacting with certain electrophiles. It also distinguishes nonpolar alkynes and polar carbonyls by cleanly inserting itself into the former but not the latter. The nucleophilicities of the two sites are also probed by DFT methods and compared with Milstein's (PNP)MgH. Although the present system shows no MLC-type H2 activation, the addition of a CS2 molecule in that way is realized. [ABSTRACT FROM AUTHOR]

Although not the only greenhouse gas, CO2 is the poster child. Unsurprisingly, therefore, there is global interest across industrial and academic research in its removal and subsequent valorisation, including to methanol and its surrogates. Although difficult to study, the heterogenous pnictogens represent one important category of catalytic materials for these conversions; their high crustal abundance and low cost offers advantages in terms of sustainability. Here, Zintl clusters based on these elements are studied as homogenous atom-precise models in CO2 reduction. A family of group 13 functionalized pnictogen clusters with the general formula [(R2E)Pn7]2– (E = B, Al, In; Pn = P, As) is synthesized and their catalytic competency in the reduction of CO2 probed. Trends in both turnover numbers and frequencies are compared across this series, and [(iBu2Al)P7]2– found to be very high-performing and recyclable. Electronic structures across the series are compared using density functional theory to provide mechanistic insights. Despite being difficult to study, heterogenous pnictogens are an important category of catalytic materials for CO2 conversion as their high crustal abundance and low cost offers advantages in terms of sustainability. Here the authors report group 13 functionalized Zintl clusters as homogenous atom-precise models in hydroborative CO2 reduction. [ABSTRACT FROM AUTHOR]

The recyclable silver-decorated magnetic Fe3O4/tannin composites Fe3O4@TA-Ag (MFTA) were prepared by hydrothermal method and characterized by XRD, XPS, TEM, and UV–Vis techniques. The catalytic and antimicrobial activities of the MFTA composites were evaluated, and it was found that the MFTA3 composite demonstrated the highest catalytic activity for the reduction of 4-nitrophenol, with a reaction rate constant of 1.039 min−1, in comparison with the other prepared composites. Furthermore, the MFTA3 composites demonstrated significant antibacterial activity toward both Escherichia coli and Staphylococcus aureus, with inhibition zones of 13.7 and 10.2 mm, respectively. This work provides promising high-performance catalysts/bactericides in environmental remediation and antibacterial applications. [ABSTRACT FROM AUTHOR]

NH3 selective catalytic reduction (NH3-SCR) is the most prevalent and effective method for removing nitrogen oxides. Over the past few decades, manganese (Mn)-based catalysts have demonstrated strong catalytic activity and have been extensively studied for low-temperature NH3-SCR reactions. This paper provides an in-depth introduction to four forms of Mn-based catalysts: single manganese oxide-based catalysts, binary Mn-based metal oxide catalysts, ternary and multivariate Mn-based metal oxide catalysts, and nano-Mn-based catalysts. Advances have been made in enhancing Mn-based catalysts' redox performance and acidity, increasing the active component's dispersion, lowering binding energy, enlarging specific surface area, raising the Mn4+/Mn3+ ratio, and enriching surface adsorbed oxygen by optimizing preparation methods, altering the oxidation state of active components, modifying crystal phases, and adjusting morphology and dispersion, along with various metal modifications. The mechanism of low-temperature NH3-SCR reactions has been elucidated using various characterization techniques. Finally, the research directions and future prospects of Mn-based catalysts for low-temperature NH3-SCR reactions are discussed, aiming to accelerate the commercial application of new Mn-based catalysts. [ABSTRACT FROM AUTHOR]

Herein we report chemoselective transfer hydrogenation (TH) of aldehydes in aqueous medium using a series of homobimetallic Ru(II) catalysts. Two homobimetallic complexes (Ru1 and Ru3) and one monometallic complex (Ru2) have been employed in the catalytic reduction of aldehydes. Bimetallic complex [(p‐cymene)2(RuCl)2L3] (Ru3) is obtained from the reaction of Schiff base ligand 2,2′‐((1E,1′E)‐((3,3′,5,5′‐tetraisopropyl‐[1,1′‐biphenyl]‐4,4′diyl)bis(azaneylylidene))bis(methaneylylidene))bis(4‐bromophenol) (H2L3) and characterized by various spectroscopic and analytical techniques. The use of formic acid/formate buffer as the hydride source and a catalyst loading of 0.01 mol % of Ru1 or Ru3 resulted in the conversion of various aldehydes to the corresponding alcohols in good to excellent yield. This method is very efficient for selective reduction of aldehydes in the presence of other reducible functional groups. A loading of 0.0001 mol % of Ru1 catalyst is sufficient to achieve a turnover frequency (TOF) of 5.5×105 h−1. Furthermore, the catalyst can been recycled and reused for six consecutives cycles without sacrificing the efficiency. A comparison of results obtained between bimetallic and monometallic complexes offers valuable insights into the distinct reactivity patterns of the bimetallic complexes, presumably originating from a cooperative effect. To understand the detailed mechanism, we have explored the mechanistic pathway using DFT methods on reported catalysts and various models which indicate that addition of aldehyde as rate‐limiting and presence of cooperativity that boost the catalytic efficiency in the case of dinuclear Ru1 catalyst. The pH dependent TH mechanism has been investigated with the aid of NMR and ESI‐MS spectroscopic techniques. [ABSTRACT FROM AUTHOR]

With the continuous expansion of industrial activities worldwide, industrial emissions of nitrogen oxides (NOx) pose a serious threat to both ecosystems and human health. Ammonia selective catalytic reduction of NO (NH3‐SCR) technology has emerged as the most effective means to reduce NOx emissions, and the development of catalysts is crucial for the successful implementation of this technology. In gas‐solid multiphase catalytic systems, the performance limitations of conventional catalysts can be effectively overcome by meticulously designing the nanostructures of the catalysts to achieve improved catalytic efficiency. In this review, the unique structural features of core‐shell structures, layered double hydroxide (LDHs), hollow nano spheres and nanotubes, along with their preparation processes, are systematically examined, beginning with the effects of structural changes on catalytic performance. Based on this review, the impact of structural modifications on the catalytic efficiency of the catalysts for the NH3‐SCR reaction and their anti‐poisoning performance were investigated. Ultimately, the influence of catalyst structural changes on the future design of catalysts is anticipated. This provides a robust scientific foundation for the conception of higher performance catalysts, paving the way for technological innovation and advancements in NOx emission reduction practices. [ABSTRACT FROM AUTHOR]

Homogeneous earth abundant transition-metal electrocatalysts capable of carbon dioxide (CO2) reduction to generate value-added chemical products are a possible strategy to minimize rising anthropogenic CO2 emissions. Previously, it was determined that Cr-centered bipyridine-based N2O2 complexes for CO2 reduction are kinetically limited by a proton-transfer step during C–OH bond cleavage. Therefore, it was hypothesized that the inclusion of pendent relay groups in the secondary coordination sphere of these molecular catalysts could increase their catalytic activity. Here, it is shown that the introduction of a pendent methoxy group favorably impacts a pre-equilibrium protonation prior to the catalytic resting state, resulting in a significant increase in catalytic activity without a loss of product selectivity for generating carbon monoxide (CO) from CO2. Interestingly, combining the pendent methoxy group with a cationic acid causes a positive shift of the catalytic reduction potential of the system, while maintaining increased activity and quantitative selectivity. This work suggests that tuning the secondary coordination sphere with respect to cationic proton sources can result in activity improvements by modifying the kinetic and thermodynamic aspects of proton transfer in the catalytic cycle. [ABSTRACT FROM AUTHOR]

In this paper, we report the synthesis of six novel triazole-based heteroscorpionate ligands based on heterocycle metathesis reactions and their iron(II) complexes. Single crystal structure analyses were performed, the spectroscopic and magnetic properties of the obtained complexes were studied and their spin crossover–structural relationships were compared to those obtained for their pyrazole-based analogues reported in the literature. In particular, the amino derivative complex bis[hydrobis(pyrazol-1-yl)(3-amino-1,2,4-triazol-1-yl)]iron(II) obtained by post-synthetic catalytic nitro-group reduction under pressure of hydrogen in an autoclave presents a scarce gradual spin crossover behavior at room temperature. The profile of the SCO curve can be explained by the presence of only relatively weak H bonds, spreading only in one dimension. Among the interesting spin transition behaviors observed for the different complexes, such stable, complete and gradual spin crossover at room temperature makes this neutral complex a good candidate for sublimation and future investigation as an active element notably for thermoreflectance-based surface microthermometry applications. [ABSTRACT FROM AUTHOR]

Commercial SSZ‐13 zeolite with different n(Si)/n(Al) ratios and from different suppliers were subjected to a post‐synthetic treatment in order to create mesopores of up to 15 nm. Furthermore, the materials were modified with copper ions and thoroughly physico‐chemically characterized. The modified textural properties varied the nature of copper species, and thus, activity in the selective catalytic reduction of NOx with ammonia (NH3‐SCR‐DeNOx). Pulsed‐field gradient nuclear magnetic resonance (PFG‐NMR) studies with hexane as probe liquid revealed improved intracrystalline diffusion for some Cu‐containing SSZ‐13 materials. The NH3‐SCR‐DeNOx pathways are verified via in situ DR UV‐Vis, in situ FT‐IR and EPR, temperature‐programmed studies as well as SSITKA studies that provide a mechanistic understanding of the reaction. Kinetic modelling results demonstrate the highest NH3‐SCR‐DeNOx reaction rates and up to 20 % lower energy barriers with n(Si)/n(Al) ratio of 6.5 for all modified forms (i. e., (NH4)Cu‐SSZ‐13_6.5 and Cu‐SSZ‐13_6.5_NaOH/0.1) and cause only negligible parasitic ammonia oxidation. The modelling of the stop‐flow experiments further demonstrates that the SCR pathway via the HONO surface intermediate is present but barely contributes to the overall NO conversion compared to the dominant path between adsorbed NH3 and NO from the gas phase. [ABSTRACT FROM AUTHOR]

The utilization of catalysts comprising metal nanoparticle has been beneficial for enhancing the performance of oxygen reduction reaction (ORR). However, the inadequate intrinsic activity of these catalysts still presents a significant challenge, limiting their overall effectiveness. This issue can be addressed by introducing single atoms, which can create a synergistic effect with the nanoparticles to catalyse and thereby improve performance. Nevertheless, the synergistic catalysis of nanoparticles and single atoms is still under investigation. In this study, we fabricated a core‐shell structured carbon framework incorporating Fe single atoms and Bi nanoparticles through the pyrolysis of COF and MOF core‐shell structures. Introducing Fe single atoms into ZIF‐8, with Fe‐ZIF‐8 as the core and Bi‐containing COF as the shell, resulted in higher ORR activity. The catalyst exhibited a half‐wave potential of 0.867 V and a high current density of 6.68 mA cm−2 in 0.1 M KOH, which were comparable to those of Pt/C equivalent. This study provides new research concepts for exploring the application of single atoms and nanoparticles in catalytic oxygen reduction reactions through synergistic effects. [ABSTRACT FROM AUTHOR]

Developing effective methods to enhance the photocatalytic hydrogen evolution activity of MoS 2 -based cocatalysts remains a challenge due to their inherently low activity. This study utilized a simultaneous vulcanization-nitrogenization solid-phase reduction method to prepare MoN 1.2x S 2-1.2x cocatalyst. The experimental and theoretical results indicate that the N-doped atoms triggered the H+ reduction catalytic activity on the (002) plane of the MoN 1.2x S 2-1.2x cocatalyst. Additionally, the MoN 1.2x S 2-1.2x cocatalyst significantly improves the hydrogen evolution reaction to form heterostructures with g-C 3 N 4 nanosheets (denoted as MoN 1.2x S 2-1.2x @g-C 3 N 4). Benefiting from the abundance of exposed catalytic sites and the excellent intrinsic charge separation characteristics of MoN 1.2x S 2-1.2x , an optimized MoN 1.2x S 2-1.2x @g-C 3 N 4 hybrid (5 wt%) exhibits an extraordinary photocatalytic H 2 evolution rate of 360.4 μmolg−1h−1, which is 19.6 and 14.3 folds higher than the g-C 3 N 4 and 5 wt% MoS 2 @g-C 3 N 4 , respectively. The simultaneous vulcanization-nitrogenization solid-phase reduction method offers a new and effective approach to dope N atoms in MoS 2 cocatalysts for photocatalytic applications. [Display omitted] • The doped N atoms triggered the catalytic activity on the (002) plane of MoS 2. • The MoN 1.2x S 2-1.2x reduces the charge transfer impedance at the interface. • The constructed heterostructure provides a transfer channel for carriers. • The 5 wt% MoN 1.2x S 2-1.2x @g-C 3 N 4 exhibits the HER of 360.4 μmolg−1h−1. [ABSTRACT FROM AUTHOR]

A Fe modified MOF-derived MnOx catalyst has been synthesized and studied for the selective catalytic reduction of NOx with NH3 (NH3-SCR). Compared with pure MnOx, Fe-modified MnOx showed a broader activity temperature window, enhanced N2 selectivity, and improved sulfur tolerance. On one hand, the incorporation of Fe into MnOx increased acidity, thereby facilitating the adsorption of NH3 as well as its activation, which plays a crucial role for the reduction of NOx. On the other hand, the presence of Fe resulted in decreased Mn4+, which contributes to improved N2 selectivity. Over Fe modified MnOx catalyst, the coordinated NH3, NH4+, bridging nitrate and bidentate nitrate are reactive, and participate in the NH3-SCR reaction following both "Eley–Rideal(E-R)" and "Langmuir–Hinshelwood(L–H)" mechanism. The present research provides an idea for broadening the activity temperature window and enhancing the sulfur tolerance of MnOx catalyst for the reduction of NOx, making it more suitable for practical application. [ABSTRACT FROM AUTHOR]

Environmental restoration because of the occurrence of harmful organic substances in our environment has received widespread attention amongst the researchers. Wastewater containing nitro-aromatic compounds and organic dyes are recently recognized as a new danger due to their toxicity towards all forms of living organisms. It is urgently needed to remove organic dye from our water systems in an efficacious manner for the purpose of both drinking and wastewater management. Binary MoS2 nanosheets@ZIF-8 nanocomposite was synthesized by hydrothermal method. The characterization techniques such as PXRD, XPS, EDS, FE-SEM, TEM, UV-DRS and PL were performed to investigate the structure, composition, morphology and optical properties of the synthesized nanocomposite. The catalytic activity of MoS2 nanosheets@ZIF-8 was tested by reduction of Picric acid (PA) in presence of NaBH4 and the photocatalytic degradation of Crystal Violet (CV) under visible-light which is not reported in any literature till date, to check the application of the synthesized nanocomposite for wastewater remediation. Original ZIF-8 had a band gap of 5.2 eV, however incorporation of MoS2 nanosheets on the ZIF-8 phase narrowed down the band gap of the MoS2 nanosheets@ZIF-8 composite to 3.2 eV. MoS2 nanosheets@ZIF-8 composite showed significantly high degradation of CV ~ 96% under visible light at optimum conditions of catalyst amount = 16 mg, dye concentration = 25 ppm and pH = 10. The degradation of CV followed first order kinetics with a first order rate constant of 0.0947 min−1. The as-synthesized catalyst showed good recyclability by showing a degradation efficiency of 85% till the fifth cycle. In addition to the photocatalytic degradation of CV, the MoS2 nanosheets@ZIF-8 displayed significantly high catalytic activity for the reduction of PA in presence of NaBH4 with a reduction efficiency of 96.26% and an apparent rate constant value of 2.7 × 10–3 s−1 in 20 min. The MoS2 nanosheets@ZIF-8 nanocomposite emerged as promising material with high catalytic activity in applications involving wastewater management. [ABSTRACT FROM AUTHOR]

Developing an efficient catalyst is the key to selective catalytic reduction (SCR) of NOx by CO (CO‐SCR) to simultaneously address the pollution of toxic NOx and CO. Herein, a novel Rh/TiO2/Ti monolithic catalyst is designed and synthesized, featuring Rh species in the form of single atoms (Rh1) and clusters (Rhn). This catalyst overcomes the inhibitory effects of oxygen, achieving low‐temperature NO conversion. The investigation substantively contributes insights into the strategic manipulation of active metal components, emphasizing the potential of single‐atom/cluster catalysts to enhance efficiency. The Rh/TiO2/Ti catalyst has demonstrated exceptional catalytic efficacy, achieving 100% NO conversion at a low temperature of 190 °C in the presence of oxygen. Additionally, it exhibits remarkable stability and water resistance for practical applications. Moreover, comprehensive characterization confirms that Rh clusters and single‐atom sites play an important role in the selective adsorption of NO and CO molecules, promoting the formation of –N2O species and ultimately resulting in the complete conversion of NO and CO to N2 and CO2. This study not only provides valuable guidance for designing high‐performance CO‐SCR catalysts but also underscores the potential of single atoms/clusters catalytic systems in both fundamental research and industrial catalysis. [ABSTRACT FROM AUTHOR]

The catalytic reduction of organic pollutants in water is a critical environmental challenge due to the persistent and hazardous nature of compounds like azo dyes and nitrophenols. In this study, we synthesized nanostructured CuO/TiO2 catalysts via a combustion technique, followed by calcination at 700 °C to achieve a rutile-phase TiO2 structure with varying copper loadings (5–40 wt.%). The catalysts were characterized using X-ray diffraction (XRD), attenuated total reflectance-Fourier transform infrared (ATR–FTIR) spectroscopy, thermogravimetric analysis-differential thermal analysis (TGA–DTA), UV-visible diffuse reflectance spectroscopy (DRS), and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDS). The XRD results confirmed the presence of the crystalline rutile phase in the CuO/TiO2 catalysts, with additional peaks indicating successful copper oxide loading onto TiO2. The FTIR spectra confirmed the presence of all the functional groups in the prepared samples. SEM images revealed irregularly shaped copper oxide and agglomerated TiO2 particles. The DRS results revealed improved optical properties and a decreased bandgap with increased Cu content, and 4-Nitrophenol (4-NP) and methyl orange (MO), which were chosen for their carcinogenic, mutagenic, and nonbiodegradable properties, were used as model organic pollutants. Catalytic activities were tested by reducing 4-NP and MO with sodium borohydride (NaBH4) in the presence of a CuO/TiO2 catalyst. Following the in situ reduction of CuO/TiO2, Cu (NPs)/TiO2 was formed, achieving 98% reduction of 4-NP in 480 s and 98% reduction of MO in 420 s. The effects of the NaBH4 concentration and catalyst mass were investigated. The catalysts exhibited high stability over 10 reuse cycles, maintaining over 96% efficiency for MO and 94% efficiency for 4-NP. These findings demonstrate the potential of nanostructured CuO/TiO2 catalysts for environmental remediation through efficient catalytic reduction of organic pollutants. [ABSTRACT FROM AUTHOR]

Mesoporous silicas of MCM-41 and MCM-48 types were synthesized and modified with copper by template ion-exchange (TIE) technique. A high dispersion of deposited copper species was managed by subsequent treatment of the samples with ammonia, urea, or acetonitrile solution. Copper-modified silicas were analysed in terms of their chemical composition (ICP-OES), ordering of porous structure (XRD), textural parameters (low-temperature N2 sorption), dispersion and form of introduced copper species (UV–vis-DR, XRD, H2-TPR, NH3-TPD). Mesoporous silicas modified with copper exhibited promising catalytic efficiency in selective catalytic reduction of NO with ammonia (NH3-SCR). The samples containing dispersed copper species (predominantly monomeric copper cations) presented enhanced catalytic activity compared to catalysts containing CuO aggregates. On the other hand, CuO aggregates showed greater catalytic activity in the side process of direct ammonia oxidation by oxygen present in the reaction mixture. It was demonstrated that TIE post-treatment of the samples with urea resulted in most effective improving dispersion of deposited copper and is less destructive for ordered porous structures of mesoporous silica comparing to treatment with ammonia solution. [ABSTRACT FROM AUTHOR]

The selective catalytic reduction (SCR) system plays a crucial role in reducing diesel exhaust emissions. To further enhance the performance of the SCR system, a three-dimensional numerical simulation model was established and experimentally validated for its reliability. Subsequently, the length (L1) and porosity (ε1) of carrier 1, as well as the length (L2) and porosity (ε2) of carrier 2, were varied to achieve an axial non-uniform distribution of the catalysts. The impact of this axial non-uniform distribution on the SCR system's performance was investigated. Finally, a fuzzy grey relational analysis method was employed to evaluate and optimize the influence of the aforementioned four individual parameters on the SCR system's denitrification (de-NOx) efficiency and pressure drop. The results indicate that variations of L1 have the greatest impact on de-NOx efficiency, while changes of ε2 have the most significant effect on pressure drop. The fuzzy grey relational degrees of L1, L2, ε1, and ε2 on de-NOx efficiency are 0.8267, 0.6288, 0.7457, and 0.8233, respectively. Similarly, the fuzzy grey relational degrees of L1, L2, ε1, and ε2 on pressure drop are 0.3552, 0.4894, 0.1045, and 0.7931, respectively. Compared with uniformly distributed catalysts, axially non-uniform distributed catalysts can improve de-NOx efficiency by 2.22% and reduce pressure drop by 46 Pa. This study provides theoretical and engineering references for improving the SCR catalyst coating process. [ABSTRACT FROM AUTHOR]

The oxygen reduction reaction (ORR) has a crucial impact on the energy conversion efficiency and the performance of fuel cells, it is urgent to deliver low‐cost efficient ORR catalysts for the aim to scale up the utilization of fuel cells. In this study, three oxamidate copper(II) complexes [Cu2(trans‐L)(H2O)2(ClO4)2]·2H2O (Cuox), [Cu2(cis‐L)(bpy)(ClO4)2]·CH3OH (Cuoxbpy), and [Cu2(cis‐L)(mebpy)(ClO4)](ClO4) (Cuoxmebpy) (L = N,N–bis(2–pyridylmethyl)oxamide, bpy = 2,2′–bipyridine, and mebpy = 4,4′–dimethyl–2,2′–bipyridine) were prepared and characterized. The configuration of L varied from the trans form to the cis form as the bipyridines were introduced to the dicopper complex. The redox properties of three oxamidate copper(II) complexes and their catalytic activities for the ORR were studied in neutral aqueous solutions. The ORR onset potentials by Cuox, Cuoxbpy, and Cuoxmebpy were 0.417, 0.502, and 0.481 versus RHE, respectively. Three complexes homogeneously catalyzed the ORR to predominantly generate H2O2. A bimolecular catalytic pathway was proposed for the ORR mediated by Cuox, whereas a single‐molecular pathway was by Cuoxbpy and Cuoxmebpy. This work demonstrated that oxamidate metal complexes are promising ORR catalyst candidates provided that their electronic structures are appropriately tuned by altering the substituent on the organic ligands. [ABSTRACT FROM AUTHOR]

A novel TiO2/CoFe2O4/SiO2 magnetic nanocomposite was successfully synthesized using sol–gel and hydrothermal methods. This nanocomposite consists of highly dispersed CoFe2O4 and TiO2 nanoparticles on the surface of the SiO2 matrix. The synthesis process involved the utilization of activated carbon, which played a dual role as a support for depositing the CoFe2O4 and TiO2 nanoparticles and as a rigid pattern for producing the silica matrix that enmeshed the nanoparticles. To study the unique characteristics of the samples, a range of analytical techniques, such as FT‐IR, VSM, XRD, SEM, N2 adsorption–desorption analysis, BET and EDX were employed. We carried out a complete examination of the catalytic performance of the TiO2/CoFe2O4/SiO2 nanocomposite for the reduction of different substances, including methyl orange (MO), safranin O (SO), methylene blue (MB), rhodamine B (RhB), chromium (VI) ions, and nitroaromatic compounds such as 2‐nitrophenol (2‐NP), 4‐nitroaniline (4‐NA), 2‐nitroaniline (2‐NA), and 4‐nitrophenol (4‐NP). The findings of our study demonstrate the remarkable efficacy of the TiO2/CoFe2O4/SiO2 nanocomposite in efficiently reducing dyes, Cr (VI), and nitroaromatic compounds to their desired forms in environmentally friendly aqueous solutions. Notably, the nanocomposite stands out due to its simple synthesis process, effortless recyclability, and its convenient separation by a magnet. [ABSTRACT FROM AUTHOR]

V2O5-WO3(MoO3)/TiO2 catalysts are widely used in industrial denitrification (deNOx) processes based on the selective catalytic reduction (SCR) technique. To lower their cost and shorten the production cycle, V2O5-MoO3/TiO2 catalysts with and without CeO2 modification were prepared using the ball milling method. This study demonstrates that the CeO2-modified catalyst has high NO conversion and a broader temperature window due to the decreased amount of easily reducible vanadium species and the enhanced property of oxygen species activation in CeO2. Meanwhile, the SO2 resistance of the catalyst is restrained due to the strong adsorption and oxidation of SO2 over CeO2 in the catalyst. [ABSTRACT FROM AUTHOR]

Sintering flue gas contains significant amounts of harmful gases, such as carbon monoxide and nitrogen oxides (NOx), which pose severe threats to the ecological environment and human health. Selective catalytic reduction (SCR) technology is widely employed for the removal of nitrogen oxides, with copper-cerium-based bimetallic catalysts and their derivatives demonstrating excellent catalytic efficiency in SCR reactions, primarily due to the significant synergistic effect between copper and cerium. This paper summarizes the main factors affecting the catalytic performance of Cu-Ce-based bimetallic catalysts and their derivatives in the selective catalytic reduction of ammonia and carbon monoxide. Key considerations include various preparation methods, doping of active components, and the effects of loading catalysts on different supports. This paper also analyzes the influence of surface oxygen vacancies, redox capacity, acidity, and specific surface area on catalytic performance. Additionally, the anti-poisoning performance and reaction mechanisms of the catalysts are discussed. Finally, the paper proposes strategies for designing high-activity and high-stability catalysts, considering the development prospects and challenges of Cu-Ce-based bimetallic catalysts and their derivatives, with the aim of providing theoretical guidance for optimizing Cu-Ce-based catalysts and promoting their industrial applications. [ABSTRACT FROM AUTHOR]

Nitrogen oxides are one of the main atmospheric pollutants and pose a threat to the ecological environment and human health. Selective catalytic reduction (NH3-SCR) is an effective way of removing nitrogen oxides, with the catalyst being the key to this technology. Two-dimensional nanostructured layered double oxide (LDO) has attracted increasing attention due to the controllability of cations in the layers and the exchangeability of anions between layers. As a derivative of layered double hydroxide (LDH), LDO not only inherits the controllability and diversity inherent in the LDH structure but also exhibits excellent performance in the catalytic field. This article contains three main sections. It begins with a brief discussion of the development of LDO catalysts and analyzes the advantages of the LDO structure. The later section introduces the synthesis methods of LDH, clarifies the conversion relationship between LDH and LDO, and summarizes the modification impacts of the properties of LDO catalysts. The application of LDO catalysts used in NH3-SCR under wild temperature conditions is discussed, and the different types, reaction processes, and mechanisms of LDO catalysts are described in the third section. Finally, future research directions and outlooks are also offered to assist the development of LDO catalysts and overcome the difficult points related to NH3-SCR. [ABSTRACT FROM AUTHOR]