Enhancement Of Catalytic Activity Research Articles

Developing Covalent Organic FrameworkBiocatalysts through Enzyme Encapsulation.

Utilizing covalent organic frameworks (COFs) as porous supports to encapsulate enzyme represents an advanced strategy for constructing COFs biocatalysts, which has inspired numerous interests across various applications. As the structural advantages including ultrastable covalent-bonded linkage, tailorable pore structure, and metal-free biocompatibility, the resultant enzyme-COFs biocatalysts showcase functional enhancement in catalytic activity, chemical stability, long-term durability, and recyclability. This Concept describes the recent advances in the methodological strategies for engineering the COFs biocatalysts, with specific emphasis on the pore entrapment and in situ encapsulation strategies. The structural advantages of the COFs hybrid biocatalysts for organic synthesis, environment- and energy-associated applications are also canvassed. Additionally, the remaining challenges and the forward-looking directions in this field are also discussed. We believe that this Concept can offer useful methodological guidance for developing active and robust COFs biocatalysts.

Exploiting Interfacial ZnO-Cu Nanocomposites in Metal–Organic Framework Derived Catalysts: Enhancement of Catalytic Activity for CO2 Hydrogenation

Exploiting Interfacial ZnO-Cu Nanocomposites in Metal–Organic Framework Derived Catalysts: Enhancement of Catalytic Activity for CO₂ Hydrogenation

Unique construction of hierarchical PANI–based nanofibrous network for boosting water electrolysis through highly efficient utilization of Pt nanocatalyst

Enhancing catalytic activity of Pt and designing rational structure of catalytic layer (CL) are effective strategies for improving the performance of proton exchange membrane water electrolysis (PEMWE) with lower Pt loading. Herein, a hierarchical nanostructured CL based on co–doped carbon, sulfonated polyaniline (PANI) nanofibrous network and Pt nanoparticles is constructed on carbon cloth by layer–by–layer in–situ growth method. The N/P/S co–doped carbon interlayer derived from PANI can promote the growth of sulfonated PANI nanofibers. The in–situ grown Pt nanoparticles is anchored by sulfonated PANI, achieving uniform and stable distribution as well as altered electronic structure for improved catalytic activity. The unique CL greatly improves the electrochemical surface area and provides interconnected pathways. The as–prepared cathode exhibits an overpotential of 23 mV at 10 mA cm−2, indicating excellent hydrogen evolution performance. Furthermore, the PEMWE device with above–mentioned cathode achieves an excellent performance of 1.771 V @ 2 A cm−2 with low Pt loading of 0.07 mg cm−2, which is comparable to that of the conventional cathode with 14 times higher Pt loading of 1 mg cm−2. Our strategy of designing hierarchical nanostructured CL provides a feasible approach to lower the consumption of Pt without performance loss for further industrialization of PEMWE.

Metallic copper-based dual-enzyme biomimetic nanoplatform for mild photothermal enhancement of anti-cancer catalytic activity

Metallic copper-based dual-enzyme biomimetic nanoplatform for mild photothermal enhancement of anti-cancer catalytic activity

A striking exploration of defect engineering in HfS2, HfSe2, and janus HfSSe through ab initio analysis for HER catalysis application

The present study emphasizes the enhancement in catalytic activity due to the formation of vacancies using dispersion corrected density functional theory. We observed that without vacancy formation, in general the edge site is an active site for hydrogen adsorption, while the lowest Gibbs free energy (ΔGH) is found to be for Janus HfSSe at the S-edge site. Furthermore, interestingly, due to the hindrance of the edge site, it facilitates only the Volmer-Heyrovsky reaction rather than the Volmer-Tafel. Among the mono vacancies, the Hafnium mono vacancy shows the lowest adsorption energy.We observed a competition between the evolution of H2S and H2 gas in the case of HfS2-VHf, whereas in the case of defected Janus and HfSe2, due to the presence of Se layers, we observed no competitiveness with H2S or H2Se gas with hydrogen gas. These defected materials exhibit lower reactional Gibbs free energy than a pristine monolayer due to its metallic nature. We observed that Hafnium vacancy enhances the HER activity, and pave the way for dominating Volmer-Heyrovsky reaction.

Enhancing catalytic activity through self-assembled hydrogen-bonded organic framework-based catalysts at liquid/liquid interface for 4-nitrophenol reduction and energy challenges in methanol fuel cell

Hydrogen-bonded organic frameworks (HOFs) are pure organic framework structures endowed with appropriate flexibility and porosity, which have attracted special attention in the field of energy and water, air, and soil remediation. In this study, six HOF-based materials were synthesized as thin film at the liquid/liquid (toluene/water) interface and characterized by FT-IR, Raman, UV–Vis, PXRD, ICP, AFM, SEM, TGA, and BET techniques. The self-assembled HOF-based thin films were employed as catalysts for the 4-nitrophenol removal from water medium and, for the first time, for methanol oxidation of fuel cell, with satisfying results. Simultaneous in situ catalyst formation and 4-nitrophenol reduction occurred in the case of Pt(0)@HOF thin film, but an extraordinary removal (not reduction) occurred in the presence of Pt(0)-trimesic acid thin film by formation of a new HOF from trimesic acid and 4-nitrophenol. Successful reduction of 4-nitrophenol occurred also in the presence of freshly prepared Pt(0)-trimesic acid, Pt(0)-melamine and Pt(0)@HOF catalysts (ex situ strategy). The chemical and thermal stability of HOF structure was improved by the interpenetration of ZIF-8 crystal structure, by increasing the hydrogen bonding and π-π stacking in the presence of 2-methylimidazole. The interpenetration of ZIF-8 to the crystal structure of HOF caused a significant decrease of the pore diameter of the structure. These pores acted as specific sites for the guest molecules, and their dimensions did not permit 4-nitrophenol to penetrate into the cavity of structures whereas allowed methanol penetration into these cavities due to its smaller size.

Enhancing catalytic activity of TiO2 nanoparticles through acid treatment in Eosin-Y sensitized photohydrogen evolution reaction system

Light-driven water splitting has gained increasing attention as an eco-friendly method for hydrogen production. There is a pressing need to enhance the performance of catalysts for the commercial viability of this reaction. Many methods have been proposed to improve catalyst performance; however, an economical and straightforward approach remains a priority. This paper presents an uncomplicated technique called acid treatment, which augments the catalytic performance of nanoparticles. The method promotes a change in the catalytic reactivity by causing a deficit in electron density of Ti and O on the surface of TiO2 nanoparticles without altering their size, morphology, or crystal structure. In the Eosin Y sensitized photocatalytic hydrogen production system, nitric acid treated TiO2 (16.95 μmol/g) exhibited 1.5 times the hydrogen production compared to bare TiO2 (11.15 μmol/g).

Design highly effective B or N doped mesoporous carbon fibers catalysts for I3-/I- redox couple regeneration in carbon-based dye-sensitized solar cells

Construction of mesoporous structure and improving the conductivity of carbon counter electrode are feasible paths to enhance the catalytic activity in dye-sensitized solar cells (DSCs) toward the I3-/I- redox couple regenerating (IRR). Herein, mesoporous carbon fiber (PCf) has been first synthesized and the DSCs using PCf counter electrode results in a power conversion efficiency (PCE) of 7.12%, significantly surpassing the PCE of 6.01% generated by the DSCs with carbon fiber (Cf) counter electrode without mesoporous structure. Additionally, doping with heteroatoms B or N can further enhance the catalytic performance of PCf. Consequently, B or N doped Cf (BPCf or NPCf) counter electrode-based DSCs achieve high PCE values of 8.43% and 7.96%, respectively, demonstrating PCE improvements of 40.3% and 32.4%. This enhancement in catalytic activity for IRR in DSCs can be first attributed to the increased specific surface area of Cf which can provide more catalytic activated sites. Meanwhile, the enhanced conductivity of PCf by heteroatoms B or N doping is also an important factor for the improved catalytic activity. This work is expected to provide potential path to enhanced the catalytic activity of carbon counter electrode in DSCs toward IRR.

The effect of magnesium embedded into NiAPO-11 zeolite on enhancing its catalytic performance of 2-butene skeletal isomerization

The distribution of acidic sites in molecular sieves has a decisive impact on catalytic skeletal isomerization of 2-butene. Accurately adjusting the acidic site to meet high selectivity and stability of the catalyst is crucial. Herein, magnesium embedding into NiAPO-11 zeolite was prepared by static hydrothermal method. The introduction of magnesium increased the proportion of weak Brønsted acid, resulting in a significant enhancement of catalytic activity. When the molar ratio of magnesium to aluminum oxide was 0.2:1, Mg-NiAPO-11 exhibited the best catalytic performance with the conversion of 2-butene being 65.06 % and the selectivity of isobutene being 71.02 %, which was comparable or even better than those reported previously. Furthermore, Mg-NiAPO-11 had good stability. The conversion of 2-butene only decreased by 3 %, while the selectivity of isobutene increased by 8 % during the 72-h reaction. Obviously, it was found that a small amount of carbon deposition led to an increase in the relative amounts of weak Brønsted acid, which resulting in an increase in the selectivity of isobutene. Our work put forward an effective strategy for accurately tuning the acidic sites of molecular sieves to effectively catalyze 2-butene to isobutene.

Optimizing Hydrogen Production: Influence of Promoters in Methane Decomposition on Titania-Modified-Zirconia Supported Fe Catalyst.

This study addresses the pivotal challenge of hydrogen production through methane decomposition, offering a pathway to achieving clean energy goals. Investigating the utilization of titania-modified zirconia dual redox supports (10TiZr) in iron or doped iron-based catalysts for the CH4 decomposition reaction, our research involves a thorough characterization process. This includes analyses of the surface area porosity, X-ray diffraction, Raman-infrared spectroscopy, and temperature-programmed reduction/oxidation. The observed sustained enhancement in catalytic activity over extended durations suggests the in situ formation of catalytically active sites. The introduction of Co or Ni into the 30Fe/10TiZr catalyst leads to the generation of a higher density of reducible species. Furthermore, the Ni-promoted 30Fe/10TiZr catalyst exhibits a lower crystallinity, indicating superior dispersion. Notably, the cobalt-promoted 30Fe/10TiZr catalyst achieves over 80% CH4 conversion and H2 yield within 3 h. Additionally, the Ni-promoted 30Fe/10TiZr catalyst attains a remarkable 87% CH4 conversion and 82% H2 yield after 3 h of the continuous process.

Photocatalytic peroxydisulfate activation for dissolved organic matter degradation in eutrophic lake water using S-scheme BiVO4/g-C3N4 3D/2D heterojunction under visible light

Large amounts of carbon are stored primarily in dissolved organic matter (DOM), which plays an important indicator of lake eutrophication. However, removing DOM from eutrophic lakes remains a major challenge. Herein, a novel S-scheme flower-like microsphere BiVO4/nanosheet g-C3N4 3D/2D heterojunction was successfully constructed using a two-step method for DOM degradation of real eutrophic lake water in the presence of peroxydisulfate (PDS). 1.0-BiVO4/g-C3N4/PDS exhibited highly efficient photocatalytic performance with an 87.8 % removal rate of DOM for 60 min, which was 5.3 and 8.9 times higher than BiVO4/PDS and g-C3N4/PDS, respectively. Sulfate radical (·SO4−), hydroxyl radical (·OH) and singlet oxygen (1O2) were mainly responsible for DOM degradation in the 1.0-BiVO4/g-C3N4/PDS system, and the transformation pathway of 1O2 was emphatically analyzed. In addition, the changes of fluorescence components in DOM were detected using synchronous fluorescence spectra, second derivative spectra, and two-dimensional correlated spectroscopy analysis. Humic-like fluorescence, fulvic-like fluorescence, and protein-like substances were removed higher than 85.30 %, 73.02 %, and 67.23 % by the 1.0-BiVO4/g-C3N4 catalyst activating the PDS under visible light (VL), respectively. When the toxicity of catalytically treated eutrophic lake water was estimated by growth inhibition of Escherichia coli, the biotoxicity of DOM decreased continuously in the BiVO4/g-C3N4/PDS/VL coupling process. Theoretical calculations and photoelectrochemical tests suggested that the BiVO4/g-C3N4/PDS catalytic activity enhancement was attributed to the S-scheme mechanism and hybrid advanced oxidation process. It is expected that this work can provide new insight into DOM degradation in eutrophic lake water by the heterogeneous photocatalysis combined with the PDS activation system.

Enhancing catalytic activity with less metal resource by regulating zeolite topology

Big-ring topology of zeolite is crucial to the catalytic activity of selective catalytic reduction (SCR) of nitrogen oxide (NOx). More works should explore how to increase the number of the big-ring topology. This work regulated ZSM-5 topologies by different acids and amino acids, exchanged Cu species into the regulated zeolites, and compared their SCR performances. L-aspartate- and L-cysteine-regulated ZSM-5 removed 67 ∼ 73 % of NO (1000 ppm, 15,000 h−1) at 150 °C. Their Cu contents were only 0.04 wt%. Under the same catalytic conditions, citric acid-regulated ZSM-5 only reached a conversion of 19 % with a Cu content of 0.15 wt%. After detailed characterizations, primary 10-membered ring (MR) on (200) plane of ZSM-5 was retained after mild treatment of the amino acids. At the same time, 5-MR on (351) and (352) planes were opened to form more 10-MR. 10-MR along (501) plane was reinforced. As a result, the 10-MR content was increased from 22 % (citric acid) to 32 % (L-aspartate and L-cysteine). The 10-MR-localized Cu was more effective than other species. Above results are in favor of understanding topology-activity relationship in zeolite. Synthesizing a more effective catalyst with less active metal is also helpful to resource saving.

Magnetic field modulation of high spin hexa-coordinated iron sites to enhance catalytic activity

The external alternating magnetic field (AMF) strategy is the most promising research topic to solve the bottleneck of catalyst activity enhancement. However, the mechanism between the arrangement of the spin electrons under the AMF and the catalytic activity enhancement for water splitting is still unclear. Herein, we synthesize Fe3O4@CNTs heterostructure as a research model and resolve the mechanism by system theoretical analysis and in-situ Raman characterization. The multiple orbital interactions of σ(dz2, pz, s) and π(dxz-px, dyz-py) promote the hexa-coordinated Feoct for both the reductive HER and oxidative OER processes. The AMF excites the transition from low to high spin configurations of the Feoct sites, which accelerates charge transfer of unpaired d electrons and optimizes adsorption and desorption interactions to intermediates during the reaction processes, resulting in a significant enhancement of the electrocatalytic activity (HER: 32 mV at 10 mA cm−2, OER: 179 mV at 100 mA cm−2).

Enhanced visible light degradation of harmful substances in wastewater by WO3/g-C3N4 heterostructured nanoparticles

The shape and energy of the photocatalyst are proven to have an impact on its photocatalytic activity. The purpose of this research is to use chemical bath deposition (CBD) technology and combine it with annealing to synthesize the WO3/g-C3N4 composite material for visible light-induced photocatalytic. A series of experiments were performed to confirm the effectiveness of the WO3/g-C3N4 photocatalyst and to study its optical chemical catalytic performance by studying the degradation reactions of metronidazole (a colorless antibiotic commonly found in a water system). These observations show that compared with each single component, WO3/g-C3N4 heterogeneous structure has an excellent enhancement in optical catalytic activity.

Atomic Strain Wave-Featured LaRuIr Nanocrystals: Achieving Simultaneous Enhancement of Catalytic Activity and Stability toward Acidic Water Splitting.

Rare earth microalloying nanocrystals have gotten widespread attention due to their unprecedented performances with customization-defected nanostructures, divided energy bands, and ensembled surface chemistry, regarded as a class of ideal electrocatalysts for oxygen evolution reaction (OER). Herein, a lanthanide microalloying strategy is proposed to fabricate strain wave-featured LaRuIr nanocrystals with oxide skin through a rapid crystal nucleation, using thermally assisted sodium borohydride reduction in aqueous solution at 60°C. The atomic strain waves with alternating compressive and tensile strains, resulting from La-stabilized edge dislocations in form of Cottrell atmospheres. In 0.5m H2SO4, the LaRuIr displays an overpotential of 184mV at 10mA cm-2, running at a steadily cell voltage for 60h at 50mA cm-2, eightfold enhancement of IrO2||Pt/C assemble in PEMWE. The coupled compressive and tensile profiles boost the OER kinetics via faster AEM and LOM pathways. Moreover, the tensile facilitates surface structure stabilization through dynamic refilling of lattice oxygen vacancies by the adsorbed oxyanions on La, Ru, and Ir sites, eventually achieving a long-term stability. This work contributes to developing advanced catalysts with unique strain to realize simultaneous improvement of activity and durability by breaking the so-called seesaw relationship between them during OER for water splitting.

Enhancement of preference, catalytic activity and thermostability of polyphenol oxidase from Rosa Chinensis by semi-rational engineering

Improvement of activity and property in polyphenol oxidases (PPOs) by protein engineering may contribute to synthesis of theaflavin (TF1) in industrial processes. Here, the potential noncatalytic residues of PPO from Rosa chinensis (RcPPO) were selected by sequence alignment, structural analysis and surface residues prediction and the mutants were gained by semi-rational site-directed mutagenesis. Mutants L173F, A174K and N334I possessed 10.48, 9.74 and 7.13 times increases respectively in preference for diphenols over monophenols. Enzymatic activity, half-life at 40 and 50 °C of the most active mutant RcPPO-FKI increased to 2.67, 2.62 and 3.37 times respectively in comparison with wild type, implying that activity and thermostability of RcPPO through mutation were improved. The improvement of activity and thermostability in the mutant should be ascribed to more hydrogen bonds formed by the conserved catalytic histidine residues with substrate, reduced fluctuation of the loop regions and increased hydrogen network of the mutational amino acids, revealed by molecular dynamics simutation and molecular docking. Moreover, the yield of TF1 was improved by catalysis of mutant RcPPO-FKI with higher synthetic efficiency of TF1 in comparison with some reported catalysts and as a promising alternative to commercial mushroom tyrosinase. PPOs with enhanced performances provide the robust candidate for industrial application.

Enhancing catalytic activity of UiO-66 through CuO nanoparticles incorporation: a study on Henry reaction and one-pot allylic C-H bond oxidation of olefins

Enhancing catalytic activity of UiO-66 through CuO nanoparticles incorporation: a study on Henry reaction and one-pot allylic C-H bond oxidation of olefins

Biochemical characterization, structure-guided mutagenesis, and application of a recombinant D-allulose 3-epimerase from Christensenellaceae bacterium for the biocatalytic production of D-allulose.

D-Allulose has become a promising alternative sweetener due to its unique properties of low caloric content, moderate sweetness, and physiological effects. D-Allulose 3-epimerase (DAEase) is a promising enzyme for D-Allulose production. However, the low catalytic efficiency limited its large-scale industrial applications. To obtain a more effective biocatalyst, a putative DAEase from Christensenellaceae bacterium (CbDAE) was identified and characterized. The recombinant CbDAE exhibited optimum activity at pH 7.5°C and 55°C, retaining more than 60% relative activity from 40°C to 70°C, and the catalytic activity could be significantly increased by Co2+ supplementation. These enzymatic properties of purified CbDAE were compared with other DAEases. CbDAE was also found to possess desirable thermal stability at 55°C with a half-life of 12.4h. CbDAE performed the highest relative activity towards D-allulose and strong affinity for D-fructose but relatively low catalytic efficiency towards D-fructose. Based on the structure-guided design, the best double-mutation variant G36N/W112E was obtained which reached up to 4.21-fold enhancement of catalytic activity compared with wild-type (WT) CbDAE. The catalytic production of G36N/W112E with 500g/L D-fructose was at a medium to a higher level among the DAEases in 3.5h, reducing 40% catalytic reaction time compared to the WT CbDAE. In addition, the G36N/W112E variant was also applied in honey and apple juice for D-allulose conversion. Our research offers an extra biocatalyst for D-allulose production, and the comprehensive report of this enzyme makes it potentially interesting for industrial applications and will aid the development of industrial biocatalysts for D-allulose.

Optimizing hydrogen-driven n-pentane isomerization over Pt-doped fibrous ZSM-5

This study focuses on developing and optimizing Pt-doped fibrous ZSM-5 catalysts for n-pentane hydroisomerization. The catalysts demonstrated improved Pt dispersion and surface area through comprehensive characterization, particularly in Pt/HFZSM-5. Catalytic evaluations revealed that Pt/HFZSM-5 exhibited remarkable hydroisomerization performance (91.9 % of conversion), surpassing commercial ZSM-5, attributed to the enhancement in physicochemical attributes like high surface area, moderate acid sites and active Pt dispersion. Notably, under optimized conditions (reaction temperature: 323.6 °C, treatment temperature: 453.7 °C, F/W ratio: 498.7 mL/g.min), Pt/HFZSM-5 achieved an impressive 92.6 % isomerization yield, signifying a substantial enhancement in catalytic activity. Mechanistic insights highlighted the pivotal role of acid sites along with hydrogen activation in hydroisomerization. The utilization of statistical modeling, response surface analysis, and experimental validation underscored the accuracy of the predictive model and its alignment with the observed outcomes (with 2.1 % variance). This work contributes to developing high-performance hydroisomerization catalysts and advances understanding of the underlying reaction mechanisms.

NiPdMo nanoparticles reduced by Cs[closo-B6H7] as high-performance catalysts for hydrogen generation from hydrolysis of ammonia borane

The synthesis of efficient catalysts for the hydrolysis of ammonia borane (NH3BH3, AB) is a matter of critical importance and immediate necessity, as it is currently considered a promising approach for the production of hydrogen. The synergy of interactions between different metals has been widely applied in the hydrolysis of AB. In this work, we first applied Cs [closo-B6H7] as the reductant to prepare a series of NixPdyMoz NPs catalysts using a simple in-situ reduction method. The structural and physical chemical properties of the as-prepared catalysts are investigated employing a multitude of various characterizations. Utilizing the optimal catalyst Ni0·3Pd0·7Mo0.2 NPs, AB hydrolysis can be completed at room temperature in just 21 s. This catalyst exhibits a lower activation energy (Ea = 52.3 kJ mol−1) and relatively higher activity (TOF = 252.7 mmolH2·mmolmetal−1min−1), which greatly outperforms many previously reported similar or corresponding catalysts. The enhancement in catalytic activity is ascribed to the moderate reducibility of Cs [closo-B6H7] and the synergistic interaction among Ni, Pd, and Mo. These results suggest the promise of multi-metal catalysts derived from Cs [closo-B6H7] for the hydrolytic dehydrogenation of hydrogen storage materials.