Performance Of Catalysts Research Articles

Regulating the electronic structure of iron sites in single-atom catalyst with interfacial chemical bond to enhance Fenton-like reaction.

Single-atom Fenton-like catalysts have been proven to be more efficient compared with aggregated catalysts due to abundant active sites. However, the low reduction rate of Fe(III) to Fe(II) remained the rate-limiting step for single-atom Fenton-like catalysts. Herein, carbon nanotubes with electron-withdrawing groups (CNTs-COOH) were combined with a single-atom catalyst (FeSAC) to fabricate a novel catalyst (FeSAC/CNTs-COOH, FCC-x). The optimal FCC-5/H2O2 system exhibited a 6.8 times higher pseudo-first-order kinetic constant of SMX degradation than that in FeSAC/H2O2 system. Additionally, the FCC-5/H2O2 system could maintain high catalytic activity within a wide pH range (4-9). The results of experiments and calculations co-verified the formation of Fe-O bonds between CNTs-COOH and FeSAC, which significantly reduced the electronic density of Fe(III) sites and further accelerated Fe(III) reduction to Fe(II), hence boosted the Fenton reaction. Quenching experiments and EPR measurements confirmed that hydroxyl radicals (⋅OH) were the primary active species responsible for pollutant degradation. The degradation pathway and toxicity analysis indicated that FCC-5/H2O2 was an eco-friendly reaction system. This study will provide a promising method for enhancing the performance of single-atom Fenton-like catalysts and offers insights into the underlying mechanisms.

Unraveling the Mechanism and Influence of Auxiliary Ligands on the Isomerization of Neutral [P,O]-Chelated Nickel Complexes for Olefin Polymerization.

The copolymerization of ethylene with polar monomers presents a significant challenge. While palladium catalysts have shown promise, nickel catalysts are more economical but suffer from poor activity. Previous studies suggest that the isomerization step involved in the nickel-catalyzed polymerization may influence the catalyst activities. Herein, we explore the isomerization mechanisms of two phosphine-phenoxide-ligated catalysts using density functional theory (DFT) studies. We found that out of dissociative, tetrahedral, and associative mechanisms, the associative mechanism is the likeliest, with a pendant methoxy oxygen atom from the ligand to fulfill the fifth coordination site on nickel before Berry pseudorotation. The effect of varying auxiliary ligands on the activation barrier heights was also investigated and found that electron-releasing alkyl groups on substituted pyridine ligands have diminished electronic influence on pseudorotational barriers, but if present at the ortho-positions, will elevate the barriers due to larger steric influences. The electron-withdrawing groups on the ligand result in weaker ligand binding and lower pseudorotational barriers. These insights into the mechanisms of cis-trans isomerization and auxiliary ligand effects may offer valuable guidance for optimizing catalyst performance in copolymerization processes by lowering the barrier of isomerization by fine-tuning the steric and electronic influences of auxiliary ligands and enhancing overall copolymerization efficiency.

Effect of Salinity on the Fe-Based Catalyst Performance during Intermittent Operation of the Ozonation Process

Effect of Salinity on the Fe-Based Catalyst Performance during Intermittent Operation of the Ozonation Process

Study on the preparation and performance of metal-supported catalyst based on biomass in situ hydrogen supply liquefaction

Study on the preparation and performance of metal-supported catalyst based on biomass in situ hydrogen supply liquefaction

Enhanced the Catalytic Performance of Samarium and Cerium Co-Modified Mn-Based Oxide Catalyst for Soot Oxidation

Manganese-based oxides with good redox properties exhibit high soot oxidation activity. To further enhance their catalytic performance, introducing additional metal elements into manganese-based oxides is considered an effective approach. Herein, two rare earth elements (Sm and Ce)-modified MnOx catalysts were prepared by the co-precipitation method. The synthesized MnOx catalyst primarily consists of the Mn3O4 phase, with trace amounts of Mn5O8. The addition of Sm or Ce maintains the predominance of the Mn3O4 phase, increases the proportion of Mn5O8, and enhances the redox properties, thereby boosting the catalytic activity for NO and soot oxidation. Notably, the coexistence of Sm and Ce achieves optimal soot oxidation activity, with T10 reaching 306 °C. Comprehensive physicochemical characterization elucidates the underlying structure–performance relationships of these catalysts.

Bi Dendrites Succeed Under Challenging Flue Gas Conditions for CO2RR

AbstractThe electrochemical reduction of carbon dioxide (ERC) from flue gas is a promising solution to mitigate CO2 emissions and importantly has the ability for direct industrial application. However, components such as N2, O2, SOx, NOx, and H2O in flue gas can hinder ERC efficiency, affecting catalyst stability and selectivity. This study systematically investigates the effect of these flue gas components on a metallic Bi dendrite catalyst. The catalyst shows remarkable stability (over 6 days are observed with constant current generation) surpassing other monometallic Bi catalysts. The active state of the catalyst has been demonstrated with operando XANES (X‐ray Absorption Near Edge Structure) analysis which has confirmed the metallic state of bismuth and notably, the catalyst performance remains unaffected despite the presence of other flue gas components such as N2, O2, SOx, and NOx. This research aims to fill a critical gap, demonstrating how flue gas components influence ERC activity and pave the way for future advancements in catalyst optimization.

Enhancing OER Activity Through Water Treatment-Induced Surface Reconstruction of Metal Surfaces.

This research introduces a simple and effective method to enhance oxygen evolution reaction (OER) performance through surface reconstruction of metal substrates via hydration. A water treatment technique is employed to form a nanometer-thick hydroxide layer on Ni foam, which significantly improved OER activity compared to pristine Ni. To further explore catalyst performance on hydrated substrates, NiFe layered double hydroxide (LDH) is deposited, resulting in NiFe LDH@hydrated Ni foam achieving superior performance and exceptional stability, maintaining 1 Acm-2 for 1000 h. In contrast, NiFe LDH@pristine Ni foam showed rapid degradation. Interestingly, while the hydrated hydroxide layer demonstrated remarkable OER activity, it is ineffective for hydrogen evolution reaction (HER). Density functional theory (DFT) calculations revealed the differing roles of hydroxides in OER and HER, providing insights into their electrochemical pathways. These findings highlight that simple hydration enhances the activity and long-term stability of LDH catalysts, addressing a key limitation in their practical use. This study demonstrates a promising and scalable strategy for improving OER performance and catalyst durability, offering valuable insights into the role of surface hydroxides in electrode reactions for energy applications.

Comparative Analysis of Durability and Performance of High-Loaded Pt Catalysts on Various Carbon Supports Using Electron Beam Reduction for Fuel Cells

Comparative Analysis of Durability and Performance of High-Loaded Pt Catalysts on Various Carbon Supports Using Electron Beam Reduction for Fuel Cells

Novel Ni/SBA-15 Catalyst Pellets for Tar Catalytic Cracking in a Dried Sewage Sludge Pyrolysis Pilot Plant

Novel Ni/SBA-15 catalysts were synthesised and their activity in the dry reforming of methane process was assessed. These materials were prepared into extrudates shaped like pellets and tested in a pyrolysis pilot plant fitted with a catalytic reactor for sewage sludge pyrolysis tar removal. The Ni/SBA-15 catalyst pellets remained highly active and stable throughout the test’s duration, converting 100% tar in the hot gas to smaller non-condensable gases, thereby increasing the pyrolysis gas fraction and eliminating the problematic tar in the vapour stream. Catalyst characterisation with Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray (EDX) analysis, Transmission Electron Microscopy (TEM), and Thermogravimetric Analysis (TGA) confirmed that both the Ni/SBA-15-powered catalyst and the pellets were resistant to sintering and carbon deposition and remained highly active even with relatively high-level sulphur in the feed stream. The Ni/SBA-15 catalyst extrudates were prepared by mixing the powdered catalyst with varied amounts of colloidal silica binder and fixed amounts of methyl cellulose and water. The highest mechanical strength of the extrudates was determined to be of those obtained with 36% of the inorganic binder. The physical properties and catalytic activity of Ni/SBA-15 pellets with 36% colloidal silica were compared with the original powdered Ni/SBA-15 catalyst to assess the binder inhibitory effect, if any. The results confirmed that colloidal silica binder did not inhibit the desired catalyst properties and performance in the reaction. Instead, enhanced catalytic performance was observed.

Breaking linear scaling relationships in oxygen evolution via dynamic structural regulation of active sites

The universal linear scaling relationships between the adsorption energies of reactive intermediates limit the performance of catalysts in multi-step catalytic reactions. Here, we show how these scaling relationships can be circumvented in electrochemical oxygen evolution reaction by dynamic structural regulation of active sites. We construct a model Ni-Fe2 molecular catalyst via in situ electrochemical activation, which is able to deliver a notable intrinsic oxygen evolution reaction activity. Theoretical calculations and electrokinetic studies reveal that the dynamic evolution of Ni-adsorbate coordination driven by intramolecular proton transfer can effectively alter the electronic structure of the adjacent Fe active centre during the catalytic cycle. This dynamic dual-site cooperation simultaneously lowers the free energy change associated with O–H bond cleavage and O–O bond formation, thereby disrupting the inherent scaling relationship in oxygen evolution reaction. The present study not only advances the development of molecular water oxidation catalysts, but also provides an unconventional paradigm for breaking the linear scaling relationships in multi-intermediates involved catalysis.

Effect of particle size on the oxygen reduction reaction activity of carbon‐supported niobium-oxide‐based nanoparticle catalysts

Abstract In this study, niobium oxynitride nanoparticles were examined to determine the effect of particle size on oxygen reduction reaction (ORR) activity. To this end, catalyst precursors with niobium oxides dispersed on carbon supports were prepared using the irradiation or impregnation method. Polyacrylonitrile was added to each precursor, followed by heat treatment under an ammonia‐containing atmosphere to synthesize niobium oxynitride nanoparticles. The structures of the prepared catalysts were analyzed using transmission electron microscopy, X-ray diffraction, and X-ray absorption spectroscopy. The results indicated that two catalysts with the same crystal phase but different particle sizes were obtained. Comparing their ORR activities revealed that the effect of particle size on ORR activity was limited. Thus, it was inferred that controlling the microelectron conduction paths can help maximize the benefits of particle size reduction. In addition, niobium oxynitride nanoparticles with different structures were obtained by varying the heat-treatment temperatures, and the ORR activity of each prepared catalyst was evaluated. These findings suggest that forming graphitized carbon residues with high electrical conductivity and controlling nitrogen-doping in the oxide nanoparticles are crucial steps for enhancing the ORR activity of oxide-based catalysts. These findings offer valuable insights for developing material design strategies to improve oxide-based catalyst performance. Graphical abstract

The construction of coupling degradation system low temperature plasma and microbiological denitrification: Interfacial reaction process and synergistic mechanism.

The degradation of antibiotic wastewater by low-temperature plasma and the removal of excess nitrogen by biological denitrification with Pseudomonas stutzeri (P. stutzeri) reducing secondary pollution has rarely been reported. In this study, iron and phenolic resin doped carbon-based porous nanofiber membranes are prepared (named RFe2-CNF) by electrostatic spinning technique, where the optimization of structure and composition endows low-temperature plasma system better catalyst performance than that of without catalyst (a 58% increase). Microbiological treatment experiments show that the plasma-degraded solution inhibits the denitrification of the P. stutzeri, but overall shows a strong denitrification effect (93.1%). In the coupling process of advanced oxidation technology and microbial denitrification technology, the possible interfacial reaction process, synergistic degradation mechanism, and products toxicity analysis are studied in detail. In addition, LC-MS and DFT are used to derive possible degradation pathways of pollutants. This work provides a new strategy to improve the degradation performance meanwhile reducing secondary pollution by low-temperature plasma-coupled microbiological treatment.

In situ formed Se-TiO2 as a highly reusable photocatalyst for selenium reduction and removal from industrial wastewater.

Selenium (Se) release from anthropogenic activities such as mining, power generation, and agriculture poses considerable environmental and ecological risks. Increasing prevalence and awareness of Se-related issues have driven the development of many innovative Se treatment technologies. Photocatalysis has shown promise towards Se removal from industrial wastewaters with minimal residuals, and is generally considered a low-cost, robust, non-toxic, and potentially solar-powered method. Despite this, its real-world application towards environmental remediation remains extremely limited. This is because research into practical considerations, such as photocatalyst stability and reusability, is often overlooked or understudied in favor of developing academically interesting but impractical materials. In this work, commercial anatase TiO2 is stress tested through fifteen cycles of reuse towards the photocatalytic reduction and removal of selenate in synthetic mining-influenced brine (SMIB) without washing or regeneration. Remarkably, selenate removal exceeds 99.3% throughout all cycles. In situ Se-TiO2 heterojunction formation, and changes to its properties including Se loading, particle size, and crystal phase, are characterized through X-ray absorption spectroscopy, scanning transmission electron microscopy, and diffuse reflectance UV/vis, while their effects on catalyst performance are elucidated. This work underscores the importance of catalyst recyclability for practical photocatalytic environmental remediation and discusses the effects of extensive use on photocatalyst performance.

Unveiling the effects of nickel loading on methane dry reforming: Perspectives from ni/fibrous Zeolite-Y catalysts

Unveiling the effects of nickel loading on methane dry reforming: Perspectives from ni/fibrous Zeolite-Y catalysts

Catalytic performance of low loading palladium-carbon catalyst in rosin disproportionation: Characterization, process enhancement, and reaction pathway

Catalytic performance of low loading palladium-carbon catalyst in rosin disproportionation: Characterization, process enhancement, and reaction pathway

Electron transfer stabilizing highly active species Mn4+ to enhance low-temperature NH3-SCR performance of MnCr composite oxide catalyst

Electron transfer stabilizing highly active species Mn4+ to enhance low-temperature NH3-SCR performance of MnCr composite oxide catalyst

Review—Meeting Fuel Cell Catalyst Requirements for Heavy-Duty Vehicle Applications

Catalyst requirements for proton exchange membrane (PEM) fuel cells differ by applications. Commercial heavy-duty vehicle (HDV) applications consume more H2 fuel and demand higher durability than many others and the total cost of ownership (TCO) of the vehicle is largely related to the performance and durability of catalysts. This article is written to bridge the gap between the industrial requirements and academic activity for advanced cathode catalysts with an emphasis on durability. From a materials perspective, the underlying nature of the carbon support, Pt-alloy crystal structure, stability of the alloying element, cathode ionomer volume fraction, and catalyst-ionomer interface play a critical role in improving performance and durability. We provide our perspective on four major approaches, namely, mesoporous carbon supports, ordered PtCo intermetallic alloys, thrifting ionomer volume fraction, and shell-protection strategies that are currently being pursued. While each approach has its merits and demerits, their key developmental needs for future are highlighted.

Study on CO Purification Performance of Copper Manganese Oxide Catalysts Used in Underground Diesel Vehicles

Study on CO Purification Performance of Copper Manganese Oxide Catalysts Used in Underground Diesel Vehicles

Insights into the exceptional support phase effect on Ag/Sm2Ce2O7: Modulating Ag distribution and Ag-support interaction to construct reactive soot oxidation catalysts

Insights into the exceptional support phase effect on Ag/Sm2Ce2O7: Modulating Ag distribution and Ag-support interaction to construct reactive soot oxidation catalysts

Tuning catalytic performance of CuZnOx catalyst via functional LaOx for catalyzing CO2 hydrogenation reaction

Tuning catalytic performance of CuZnOx catalyst via functional LaOx for catalyzing CO2 hydrogenation reaction