Catalyst Longevity Research Articles

Data-Driven Approaches for Predicting Catalyst Performance in CO2 Hydrogenation

This paper explores the critical role of data collection and preparation in leveraging machine learning techniques for predicting catalyst performance in CO2 hydrogenation processes. As the global community seeks sustainable solutions to mitigate carbon emissions, understanding the efficiency of catalysts in converting CO2 into valuable chemicals becomes increasingly important. The study discusses various types of data utilized in this context, including both experimental and simulation data, while highlighting their significance in comprehensively understanding key factors such as reaction rates, selectivity, and catalyst stability. For instance, the ability of a catalyst to selectively produce desired products over others can significantly impact the overall economic viability of CO2 hydrogenation processes. Furthermore, stability data sheds light on the longevity and durability of catalysts, revealing insights into deactivation mechanisms that can occur due to factors like sintering, poisoning, or leaching of active sites. On the other hand, simulation data generated from advanced computational methods such as density functional theory (DFT) and molecular dynamics (MD) provides a deeper understanding of the electronic and structural properties of catalysts. These computational techniques allow researchers to predict reaction pathways, activation energies, and the behavior of intermediate species, thereby complementing experimental findings and guiding the design of more effective catalysts. The paper also emphasizes the importance of utilizing publicly available databases and collaborative research datasets, which serve to enhance data accessibility and foster scientific collaboration among researchers in the field. By pooling resources and sharing findings, the scientific community can accelerate the discovery and optimization of novel catalysts. Additionally, the study outlines essential steps in the data preparation process, including rigorous data cleaning, preprocessing, and feature selection, all of which are crucial for ensuring the quality and reliability of the data used in machine learning models. The paper discusses the implementation of cross-validation techniques and performance metrics that help evaluate and validate model predictions, ensuring that the developed models generalize well to unseen data.

In-situ observation of defects evolution of graphene nanoflakes in Pt/C catalyst for boosting ORR performance

The structural stability of supported metal nanoparticles determines the activity and longevity of heterogeneous catalysts. Unfortunately, the chemical/thermal working environment inevitably accelerates metal sintering to larger crystallites that leads to the degradation of catalytic performance. Here, we demonstrate that the distribution of defects in carbon support as an inherent parameter plays a crucial role in catalyst sintering. Based on in-situ transmission electron microscopy studies, the strong metal-support interaction between platinum (Pt) nanoparticles and defect-rich graphene nanoflakes largely suppresses metal sintering up to 700 °C. Particularly, the optimal carbon support can be achieved in the annealing process, in which the mass transfer and charge transport can be enhanced by accurately manipulating the distribution of defects in carbon matrix and graphitization degree. It is worth noting that the screened Pt/GNs-300 exhibits impressive oxygen reduction reaction performance with high half-wave potential (0.91 V), mass activity (108.1 A g–1Pt) and excellent stability. By its ascendancy in ORR, the Pt/GNs-300 exhibits a high open-circuit voltage of 1.41 V and a maximum power density of 198.6 mW cm−2 in Zn-air battery, implying its brilliant practicability. This work paves a pathway for achieving sinter-resistant metal-loaded catalysts in energy electrocatalysis.

Integrating renewable energy with fuel synthesis: Conceptual framework and future directions

The integration of renewable energy sources with fuel synthesis represents a transformative approach to addressing the twin challenges of energy sustainability and climate change. This review presents a conceptual framework for coupling renewable energy technologies, such as solar, wind, and biomass, with fuel synthesis processes to produce sustainable, zero-carbon fuels. The framework emphasizes the use of renewable electricity for water splitting and carbon dioxide reduction, key steps in synthesizing hydrogen and other synthetic fuels. The conceptual framework highlights the importance of advanced catalysts in enhancing the efficiency and selectivity of these chemical reactions. Innovations in nanostructured catalysts, hybrid materials, and biomimetic approaches are discussed for their potential to significantly improve the performance and durability of catalytic processes. Additionally, the framework underscores the role of advanced characterization techniques and computational modeling in understanding and optimizing catalyst behavior. This integration necessitates addressing technical challenges associated with scaling up production processes from laboratory to industrial levels. These challenges include ensuring the stability and longevity of catalysts under operational conditions, managing the intermittency of renewable energy sources, and developing robust systems for capturing and utilizing carbon dioxide. Furthermore, the economic viability of these integrated systems is critical, requiring cost-effective solutions that leverage earth-abundant materials and optimize the overall energy efficiency. The environmental benefits of integrating renewable energy with fuel synthesis are substantial, offering a pathway to significantly reduce carbon emissions and reliance on fossil fuels. The production of synthetic fuels using renewable energy can lead to a closed carbon cycle, thereby mitigating the impact on climate change and contributing to a sustainable energy future. Future directions in this field involve interdisciplinary research to further enhance catalyst performance, develop new materials, and refine process integration strategies. A roadmap for future development includes prioritizing areas such as improved catalyst design, efficient CO2 capture technologies, and the integration of electrochemical and photochemical systems. This abstract concludes by underscoring the transformative potential of renewable energy-fuel synthesis integration, envisioning a future where sustainable energy practices become the cornerstone of global energy systems. Keywords: Integrating, Renewable Energy, Fuel Synthesis, Future Directions, Framework.

Kinetic modeling of dual-stage oxidative extractive denitrogenation of model fuel

The petroleum fraction of crude oil is laden with notorious nitrogen compounds, whose removal facilitates fuel oil transport and enhances the longevity of hydrodesulfurization catalysts. Petroleum refining operation thus demands the adoption of unconventional techniques, such as coupled oxidative–extractive denitrogenation. Kinetic models can provide insights into the reaction mechanism and the design and performance of reactors. In this work, nine different kinetic models were developed by applying the Langmuir–Hinshelwood and Eley–Rideal approaches to various reaction pathways. The screening of the kinetic models was done based on the values of the rate law parameters and corresponding R 2 and adjusted R 2 values calculated through a multi-parametric, non-linear regression based on the Levenberg–Marquardt algorithm. Out of all the models, the Eley–Rideal model corresponding to the rate expression rs9 was found to be the best fit, reflecting that hydrogen peroxide remained in bulk while pyridine alone was adsorbed on the catalyst. The selection of suitable extractants for the extractive removal of oxidation products was made based on their extraction efficiency and partition coefficients. The ternary liquid–liquid equilibrium (LLE) data for the (acidulated water-pyridine-isooctane) and (acidulated water-pyridine N-oxide-isooctane) systems were plotted, and Othmer–Tobias, Hand, and Bachman correlations explained the consistency of the experimental LLE data.

A Review on the Development of Polymer Supported Heterogeneous Palladium Materials for Organic Synthesis and Electrochemical Applications

Abstract:: This comprehensive review explores the advancements in catalytic transformation, focusing on the use of heterogeneous catalytic systems with a particular emphasis on polymeric-supported palladium (Pd) complexes. This study explores the limitations associated with conventional homogeneous reagents, emphasizes the transition to eco-friendly catalytic systems, and emphasizes the importance of Pd nanoparticles. These nanoparticles are particularly noteworthy for their distinctive properties, including elevated catalytic activity, making them promising for various applications in organic synthesis. The review thoroughly examines the design and synthesis of heterogeneous catalysts, emphasizing the crucial selection of safe and recyclable supports to augment the longevity and reusability of metallic catalysts. Diverse polymer varieties, including polystyrene (PS), polyethylene (PE), polyacrylate derivatives, polyethylene glycol (PEG), and grafted polymers, are investigated as viable supports for Pd complexes. The authors intricately describe the synthesis techniques for these polymer-supported Pd catalysts and furnish illustrative examples showcasing their effectiveness in organic transformation. This comprehensive review additionally highlights the synthesis of polymer-supported palladium (Pd) materials and discusses their applications in electrochemistry. The focus extends to the electrocatalytic properties of Pdbased polymeric nanomaterials, showcasing their effectiveness in glucose sensing, hydrogen peroxide detection, and the sensing of other biological analytes. Furthermore, the catalytic capabilities of Pd nanoparticles in various electrochemical applications, including wastewater treatment and electrochemical capacitors, are explored. Integrating polymer-supported Pd materials into these electrochemical processes underscores their versatility and potential contributions to advancements in catalysis and electrochemical sensing. Catalytic applications featuring polymer-supported palladium complexes with polymeric ligands in organic synthesis processes use the Sonogashira reaction, Suzuki-Miyaura coupling, Heck reaction, Catalytic asymmetric transformations, etc. The subsequent section of the paper focuses on the creation of polymeric palladium complexes, achieved by the complexation of polymeric ligands with palladium precursors. It delves into noteworthy examples of catalytic processes employing polymer-supported palladium complexes featuring polymeric ligands, emphasizing distinct polymers, such as PS, PE, polyacrylate derivatives, PEG, and grafting polymers. The review concludes by exploring catalytic asymmetric transformations using chiral palladium complexes immobilized on polymer supports and discusses various chiral ligands and their immobilization on polymer supports, emphasizing their application in asymmetric allylic alkylation. The review furnishes a comprehensive summary of recent advancements, challenges, and prospective avenues in catalytic oxidation facilitated by polymer- supported palladium catalysts with electrochemical applications.

Green and sustainable use of macadamia nuts as support material in Pt-based direct methanol fuel cells

The successful commercialization of direct methanol fuel cells (DMFCs) is hindered by inadequate methanol oxidation activity and anode catalyst longevity. Efficient and cost-effective electrode materials are imperative in the widespread use of DMFCs. While Platinum (Pt) remains the primary component of anodic methanol oxidation reaction (MOR) electrocatalysts, its utilization alone in DMFC systems is limited due to carbon monoxide (CO) poisoning, instability, methanol crossover, and high cost. These limitations impede the economic feasibility of Pt as an electrocatalyst. Herein, we present the use of powdered activated carbon (PAC) and granular activated carbon (GAC), both sourced from macadamia nut shells (MNS), a type of biomass. These bio-based carbon materials are integrated into hybrid supports with reduced graphene oxide (rGO), aiming to enhance the performance and reduce the production cost of the Pt electrocatalyst. Electrochemical and physicochemical characterizations of the synthesized catalysts, including Pt-rGO/PAC-1:1, Pt-rGO/PAC-1:2, Pt-rGO/GAC-1:1, and Pt-rGO/GAC-1:2, were conducted. X-ray diffraction analysis revealed crystallite sizes ranging from 1.18 nm to 1.68 nm. High-resolution transmission electron microscopy (HRTEM) images with average particle sizes ranging from 1.91 nm to 2.72 nm demonstrated spherical dispersion of Pt nanoparticles with some agglomeration across all catalysts. The electrochemical active surface area (ECSA) was determined, with Pt-rGO/GAC-1:1 exhibiting the highest ECSA of 73.53 m2 g−1. Despite its high ECSA, Pt-rGO/GAC-1:1 displayed the lowest methanol oxidation reaction (MOR) current density, indicating active sites with poor catalytic efficiency. Pt-rGO/PAC-1:1 and Pt-rGO/PAC-1:2 exhibited the highest MOR current densities of 0.77 mA*cm−2 and 0.74 mA*cm−2, respectively. Moreover, Pt-rGO/PAC-1:2 and Pt-rGO/PAC-1:1 demonstrated superior electrocatalytic mass (specific) activities of 7.55 mA/mg (0.025 mA*cm−2) and 7.25 mA/mg (0.021 mA*cm−2), respectively. Chronoamperometry tests revealed Pt-rGO/PAC-1:2 and Pt-rGO/PAC-1:1 as the most stable catalysts. Additionally, they exhibited the lowest charge transfer resistances and highest MOR current densities after durability tests, highlighting their potential for DMFC applications. The synthesized Pt supported on PACs hybrids demonstrated remarkable catalytic performance, stability, and CO tolerance, highlighting their potential for enhancing DMFC efficiency.

Critical Review of Pd-Catalyzed Reduction Process for Treatment of Waterborne Pollutants.

Catalyzed reduction processes have been recognized as important and supplementary technologies for water treatment, with the specific aims of resource recovery, enhancement of bio/chemical-treatability of persistent organic pollutants, and safe handling of oxygenate ions. Palladium (Pd) has been widely used as a catalyst/electrocatalyst in these reduction processes. However, due to the limited reserves and high cost of Pd, it is essential to gain a better understanding of the Pd-catalyzed decontamination process to design affordable and sustainable Pd catalysts. This review provides a systematic summary of recent advances in understanding Pd-catalyzed reductive decontamination processes and designing Pd-based nanocatalysts for the reductive treatment of water-borne pollutants, with special focus on the interactions and transformation mechanisms of pollutant molecules on Pd catalysts at the atomic scale. The discussion begins by examining the adsorption of pollutants onto Pd sites from a thermodynamic viewpoint. This is followed by an explanation of the molecular-level reaction mechanism, demonstrating how electron-donors participate in the reductive transformation of pollutants. Next, the influence of the Pd reactive site structure on catalytic performance is explored. Additionally, the process of Pd-catalyzed reduction in facilitating the oxidation of pollutants is briefly discussed. The longevity of Pd catalysts, a crucial factor in determining their practicality, is also examined. Finally, we argue for increased attention to mechanism study, as well as precise construction of Pd sites under batch synthesis conditions, and the use of Pd-based catalysts/electrocatalysts in the treatment of concentrated pollutants to facilitate resource recovery.

Post‐Synthetic Ensembling Design of Hierarchically Ordered FAU‐type Zeolite Frameworks for Vacuum Gas Oil Hydrocracking

AbstractZeolites hold importance as catalysts and membranes across numerous industrial processes that produce most of the world's fuels and chemicals. In zeolite catalysis, the rate of molecular diffusion inside the micropore channels defines the catalyst's longevity and selectivity, thereby influencing the catalytic efficiency. Decreasing the diffusion pathlengths of zeolites to the nanoscopic level by fabricating well‐organized hierarchically porous architecture can efficiently overcome their intrinsic mass‐transfer limitations without losing hydrothermal stability. We report a rational post‐synthetic design for synthesizing hierarchically ordered FAU‐type zeolites exhibiting 2D‐hexagonal (P6mm) and 3D‐cubic (Ia d) mesopore channels. The synthesis involves methodical incision of the parent zeolite into unit‐cell level zeolitic fragments by in situ generated base and bulky surfactants. The micellar ensembles formed by these surfactant‐zeolite interactions are subsequently reorganized into various ordered mesophases by tuning the micellar curvature with ion‐specific interactions (Hofmeister effect). Unlike conventional crystallization, which offers poor control over mesophase formation due to kinetic constraints, crystalline mesostructures can be developed under dilute, mild alkaline conditions by controlled reassembly. The prepared zeolites with nanometric diffusion pathlengths have demonstrated excellent yields of naphtha and middle‐distillates in vacuum gas oil hydrocracking with decreased coke deposition.

Post-Synthetic Ensembling Design of Hierarchically Ordered FAU-type Zeolite Frameworks for Vacuum Gas Oil Hydrocracking.

Zeolites hold importance as catalysts and membranes across numerous industrial processes that produce most of the world's fuels and chemicals. In zeolite catalysis, the rate of molecular diffusion inside the micropore channels defines the catalyst's longevity and selectivity, thereby influencing the catalytic efficiency. Decreasing the diffusion pathlengths of zeolites to the nanoscopic level by fabricating well-organized hierarchically porous architecture can efficiently overcome their intrinsic mass-transfer limitations without losing hydrothermal stability. We report a rational post-synthetic design for synthesizing hierarchically ordered FAU-type zeolites exhibiting 2D-hexagonal (P6mm) and 3D-cubic (Ia d) mesopore channels. The synthesis involves methodical incision of the parent zeolite into unit-cell level zeolitic fragments by in situ generated base and bulky surfactants. The micellar ensembles formed by these surfactant-zeolite interactions are subsequently reorganized into various ordered mesophases by tuning the micellar curvature with ion-specific interactions (Hofmeister effect). Unlike conventional crystallization, which offers poor control over mesophase formation due to kinetic constraints, crystalline mesostructures can be developed under dilute, mild alkaline conditions by controlled reassembly. The prepared zeolites with nanometric diffusion pathlengths have demonstrated excellent yields of naphtha and middle-distillates in vacuum gas oil hydrocracking with decreased coke deposition.

Morphology of RuO2(110) Films during Electrochemistry

RuO2 is a well-known electrocatalyst for the oxygen evolution reaction (OER), a critical electrochemical reaction in the water electrolyzer. The behavior of RuO2 during the OER is, however, a subject of debate, in particular, the corrosion mechanism. In this contribution, we report an electrochemical AFM (EC-AFM) study on well-defined RuO2 films grown using molecular beam epitaxy (MBE). We track the morphology of step edges prior, during, and after the OER in acid and alkaline electrolytes to gain insights into the corrosion behavior. Our EC-AFM experiment shows the potential range of RuO2 corrosion and hints at the role of strain and defects in the RuO2 stability. The heterogeneity of corrosion will be discussed in the context of the catalyst longevity along with possible mitigation strategies.

Analysis of Electrocatalytic Performance of Nanostructured MoS2 in Hydrogen Evolution Reaction

Abstract: Recently, renewable and non-conventional energy production methods have been getting widespread attention. Fast research progress in establishing green energy indicates the relevance of carbon-free power production. Chemical energy stored in hydrogen molecules is considered green energy to substitute conventional energy sources. It is possible to produce hydrogen without carbon emission by water electrolysis. The action of appropriate catalysts can increase the rate of water electrolysis. Among various non-harmful and cost-effective catalysts, MoS2 nanostructures emerge as electrocatalysts in water electrolysis. This paper reviews the electrocatalytic properties of nanostructures of MoS2 by analyzing different characterization techniques used in water electrolysis, such as linear sweep voltammetry, cyclic voltammetry, and electrochemical impedance spectroscopy and chronopotentiometry. This article explores the relationship between electrocatalytic characteristics and the reaction mechanism. How the reaction kinetics of electrocatalyst varies with respect to the structural changes of MoS2 nanostructures, pH of surrounding medium and longevity of catalyst are analysed here. It is found that the 1T phase of MoS2 has faster catalytic activity than the 2H phase. Similarly, among the various shapes and sizes of MoS2 nanostructures, quantum dot or monolayer structures of MoS2 and doped version of MoS2 have better catalytic activity. Acidic electrolyte shows better kinetics for releasing hydrogen than other pH conditions. Longevity, catalytic behaviour over a wide pH range, cost-effective synthesis methods and non-toxicity of MoS2 catalysts suggest its future scope as a better catalyst for commercial purposes. Electrocatalytic activity, stability, future scope and challenges of various MoS2 nanostructures are reviewed here.

The Activity and Stability of Promoted Cu/ZnO/Al2O3 Catalyst for CO2 Hydrogenation to Methanol

Cu/ZnO/Al2O3 catalyst with the addition of tri-promoters (Mn/Nb/Zr) was investigated with respect to their catalytic activity and stability in a prolonged reaction duration in methanol synthesis. Spent catalysts were characterized using N2 adsorption-desorption, FESEM/EDX, TEM, N2O chemisorption, and XPS for their physicochemical properties. The catalyst longevity study was evaluated at two days, seven days, and 14 days at 300 °C, 31.25 bar, 2160 mL/g.hr GHSV, and H2:CO2 at 10:1. The CO2 conversion and methanol yield decreased by about 5.7% and 7.7%, respectively, when the reaction duration was prolonged to 14 days. A slight reduction in catalytic activity under prolonged reaction duration was found due to thermal degradation.

Catalytic Distillation of Atmospheric Residue of Petroleum over HY-MCM-41 Micro-Mesoporous Materials

Catalytic distillation is a technology that combines a heterogeneous catalytic reaction and the separation of reactants and products via distillation in a single reactor/distillation system. This process combines catalysis, kinetics, and mass transfer to obtain more selective products. The heterogeneous catalyst provides the sites for catalytic reactions and the porous surface for liquid/vapor separation. The advantages of catalytic distillation are energy savings, low waste streams, catalyst longevity, higher conversion, and product selectivity; these properties are interesting for petrochemical and petroleum industries. For this study, 100 mL of atmospheric residue of petroleum (ATR) was distilled in the presence of 1.0 g of a micro/mesoporous catalyst composed of a HY-MCM-41, and the reactor used was an OptiDist automatic distillation device, operating according to ASTM D-86 methodology. The products were collected and analyzed by gas chromatography. The samples of ATR, HY/ATR, and HY-MCM-41/ATR were analyzed by thermogravimetry (TG) to determine the activation energies (Ea) relative to the thermal decomposition of the process, using the Ozawa–Flynn–Wall (OFW) kinetic model. The obtained results show a potential catalytic distillation system for use in the reaction of heavy petroleum fractions and product separation from the HY/MCM-41 micro/mesoporous catalyst. The TG data revealed two mass loss events for ATR in the ranges of 100–390 and 390–590 °C, corresponding to volatilization and thermal cracking, respectively. The Ea determined for the thermal degradation of the ATR without a catalyst was in the range of 83–194 kJ/mol, whereas in the presence of the HY-MCM-41 catalyst, it decreased to 61–105 kJ/mol, evidencing the catalytic effect of the micro-mesoporous material. The chromatography analysis allowed for the identification of gasoline and a major production of diesel and gasoil when the HY-MCM-41 mixture was used as the catalyst, evidencing the synergism of the combined effect of the acid sites, the crystalline phase, and the microporosity of the HY zeolite with the accessibility of the hexagonal mesoporous structure of the MCM-41 material.

Atomically dispersed Fe–N4 moieties in porous carbon as efficient cathode catalyst for enhancing the performance in microbial fuel cells

Microbial fuel cells (MFCs) play significant role in solving energy crisis and water pollution, while their scale-up is restricted by the sluggish oxygen reduction reaction (ORR) on the cathode. Herein, the influence of different metal and nitrogen co-doped porous carbon (Fe-NpC, Mn-NpC and Ni-NpC) on the ORR reactivity are investigated, which is obtained in the following order: Fe-NpC > Mn-NpC > Ni-NpC. The X-ray absorption spectroscopy verifies the Fe-NpC catalyst having atomically dispersed Fe–N4 moieties. The Fe-NpC catalyst exhibits an ultrahigh specific surface area of 2099 m2 g−1 and splendid ORR performance with a rather positive half wave potential of 0.902 V in alkaline and 0.705 V (vs. Reversible Hydrogen Electrode) in neutral electrolytes. The excellent ORR characteristic provides sufficient feasibility for Fe-NpC as cathode catalyst to construct MFC. The Fe-NpC-MFC performs the highest power density of 1793 ± 77 mW m−2, open circuit voltage of 775 mV, favorable output stability of 6.0% decline in 430 h, and chemical oxygen demand removal of 90.3 ± 4.3%, all surpassing the benchmark Pt/C-MFC. This study demonstrates that the combination of the longevity of Fe-NpC catalyst with its atomically dispersed Fe–N4 structure can ensure a stable and long-term application in MFCs treating wastewater.

Cyclopentadienone Iron Complex-Catalyzed Hydrogenation of Ketones: An Operando Spectrometric Study Using Pressurized Sample Infusion-Electrospray Ionization-Mass Spectrometry

The sulfonate charge-tagged cyclopentadienone iron complexes [FeR(MeCN)(CO)2-SO3]Na (R = TMS, tBu) were prepared and used for mechanistic investigations using pressurized sample infusion-electrospray ionization-mass spectrometry in the hydrogenation of acetophenone. Reactions were conducted in a mixed aqueous/alcoholic solvent. Based on kinetic and mass spectrometric experiments, information about the operating reaction mechanism was obtained. Furthermore, analysis of the kinetic profiles and mass spectra indicated catalyst decomposition. By analysis of the mass spectrometric results, the decomposition cascade was found to start by solvolysis of the trimethylsilyl (TMS) groups flanking the carbonyl group in the cyclopentadienone ligand of the catalyst. Subsequent dimerization, comproportionation to form Fe(I) radical species, and formation of catalytically inactive iron tricarbonyl species were observed, limiting the catalyst lifetime. Replacement of the TMS groups by non-hydrolyzable tert-butyl groups leads to a significant increase in the observed turnover frequency and catalyst longevity. The turnover number, determined to be approximately 65 under standardized reaction conditions, could be increased to >1000 by the mechanism-guided structural change in the catalyst. No compounds corresponding to Fe(I) species or dimerization products could be identified in this case. The present study suggests that for hydrogenations with cyclopentadienone iron complexes, the use of alkyl groups flanking the C═O double bond in the ligand is beneficial over the use of silyl groups when conducted in aqueous media.

An Imidazole‐Rich Pd(II)‐Polymer Pre‐catalyst for the Suzuki‐Miyaura Coupling: Stability Influenced by Dissolved Oxygen and Reactants Concentration

AbstractHerein a novel Pd(II)‐polymeric pre‐catalyst was prepared by coordinating Pd(II) ions to a low cost imidazole/carboxylate‐rich polymer. The material displays good activity in the Suzuki‐Miyaura coupling towards a range of aryl bromides and iodides in iPrOH/H2O mixtures at 25 or 60 °C. Catalyst longevity and recyclability proved to be sensitive to the concentration of the cross‐coupling partners. When the concentration of PhBr is high ([PhBr]=250 mmol L−1), inactive Pd(0) aggregates were detected. On the other hand, when the reaction was performed at 20‐fold dilution ([PhBr]=12.5 mmol L−1) the material could be reused up to 12 times without significant loss of catalytic activity. In this condition, minimum amount of Pd(0) was detected by XPS analysis and no Pd(0) aggregates were observed by XRPD. Importantly, it was found that the presence of oxygen is fundamental for avoiding formation of inactive Pd(0) aggregates.

A Hybrid Microbial–Enzymatic Fuel Cell Cathode Overcomes Enzyme Inactivation Limits in Biological Fuel Cells

The construction of optimized biological fuel cells requires a cathode which combines the longevity of a microbial catalyst with the current density of an enzymatic catalyst. Laccase-secreting fungi were grown directly on the cathode of a biological fuel cell to facilitate the exchange of inactive enzymes with active enzymes, with the goal of extending the lifetime of laccase cathodes. Directly incorporating the laccase-producing fungus at the cathode extends the operational lifetime of laccase cathodes while eliminating the need for frequent replenishment of the electrolyte. The hybrid microbial–enzymatic cathode addresses the issue of enzyme inactivation by using the natural ability of fungi to exchange inactive laccases at the cathode with active laccases. Finally, enzyme adsorption was increased through the use of a functionally graded coating containing an optimized ratio of titanium dioxide nanoparticles and single-walled carbon nanotubes. The hybrid microbial–enzymatic fuel cell combines the higher current density of enzymatic fuel cells with the longevity of microbial fuel cells, and demonstrates the feasibility of a self-regenerating fuel cell in which inactive laccases are continuously exchanged with active laccases.

Highly Efficient Ethenolysis and Propenolysis of Methyl Oleate Catalyzed by Abnormal N-Heterocyclic Carbene Ruthenium Complexes in Combination with a Phosphine–Copper Cocatalyst

Fluorinated imidazo[1,5-a]pyridine abnormal carbene ruthenium complexes (F-aImPy–Ru) with a tricyclohexylphosphine copper chloride (Cy3P–CuCl) cocatalyst were developed for the ethenolysis/propenolysis of methyl oleate. These catalysts showed remarkable catalytic efficiencies (turnover numbers of 100,000 for ethenolysis and 200,000 for propenolysis) and excellent α-olefin selectivity (up to 99%). A computational study indicated that the energy barrier of the β-hydride elimination pathway in the presence of a phosphine–copper cocatalyst is higher than that in the absence of the cocatalyst, which might contribute to the improved longevity of the ruthenium catalyst in the reaction.

Structured hierarchical Mn–Co mixed oxides supported on silicalite-1 foam catalyst for catalytic combustion

Silicalite-1 (S1) foam was functionalized by supporting manganese–cobalt (Mn–Co) mixed oxides to develop the structured hierarchical catalyst (Mn–[email protected]) for catalytic combustion for the first time. The self-supporting S1 foam with hierarchical porosity was prepared via hydrothermal synthesis with polyurethane (PU) foam as the template. Subsequently, Mn–Co oxide nano sheets were uniformly grown on the surface of S1 foams under hydrothermal conditions to prepare the structured hierarchical catalyst with specific surface area of 354 m2·g−1, micropore volume of 0.141 cm3·g−1 and total pore volume of 0.217 cm3·g−1, as well as a good capacity to adsorb toluene (1.7 mmol·g−1 at p/p0 = 0.99). Comparative catalytic combustion of toluene of over developed structured catalyst Mn–[email protected] was performed against the control catalysts of bulk Mn–[email protected] (i.e., the crushed Mn–[email protected]) and unsupported Mn–Co oxides (i.e., Mn–Co). Mn–[email protected] exhibited comparatively the best catalytic performance, that is, complete and stable toluene conversion at 248 °C over 65 h due to the synergy between Mn–Co oxides and S1 foam, which provided a large number of oxygen vacancies, high redox capacity. In addition, the hierarchical porous structure also improved the accessibility of active sites and facilitated the global mass transfer across the catalyst bed, being beneficial to the catalysis and catalyst longevity.

Effect of Mesoporosity on Methanol‐to‐Olefin Reactions over Organosilane‐Directed Mesoporous SSZ‐13 Zeolites

A suitable balance between microporosity and mesoporosity is required to attain MTO catalyst longevity with high olefin selectivity.