Catalytic Effect Research Articles

Efficient photocatalytic degradation of tetracycline and its derivatives by green recyclable PAN/Bi2WO6/Cu2O nanofiber membrane

The use of tetracycline antibiotics in industry, healthcare, animal husbandry, agriculture, and aquaculture has resulted in excessive concentrations in a variety of aquatic environments. In this work, PAN/Bi2WO6/Cu2O nanofibrous membranes (PBC ENMs) with photocatalytic degradation performance were successfully prepared using electrostatic spinning technique, and the morphology of catalysts and PBC ENMs were characterised by SEM, BET and UV–Vis. The results demonstrated that the prepared nanofibrous membranes could achieve 97.05 % photocatalytic degradation of TC under visible light, and the degradation efficiencies of its derivatives, chlortetracycline (CTC) and oxytetracycline (OTC), reached 90.87 % and 85.12 %, respectively. Free radical trapping experiments and mechanistic analyses showed that·O2– is the main active factor in the degradation process. The highest degradation rate of 97.05 % was achieved at initial pH = 7.2.PBC ENMs adsorbed above 87.5 % after six cycles of the experiment. The highest degradation rate of 97.05 % was achieved at initial pH = 7.2 PBC ENMs adsorbed above 87.5 % after six cycles of the experiment. Based on the above advantages, the preparation process of PBC ENMs is simple, low-cost and has good catalytic effect, which provides a simple and efficient treatment means for the treatment of TC wastewater and has a broad application prospect.

Study of Heavy Oil In-situ Combustion with Copper Biocatalysts: Kinetics and Thermodynamic Aspects of High-Temperature Oxidation Reactions

In-situ combustion is considered an efficient thermally enhanced oil recovery method. However, the combustion front stabilization remains a challenge for the scientific community. The present study examines the efficacy of copper tall oil (Cu-TO) and copper sunflower oil (Cu-SFO) on heavy oil high-temperature oxidation reactions, which are believed to solve this challenge. We applied non-isothermal differential scanning calorimetry (DSC) analyses combined with an isoconversional kinetic approach in order to calculate kinetic parameters, thermodynamic functions, and the effective rate constant of these reactions. The obtained results demonstrated that both catalysts are able to reduce the activation energies and shift oxidation regions to lower temperatures, with Cu-SFO showing superior performance. Kinetic predictions further supported these findings and revealed that the selected catalysts contributed significantly to decreasing oxidation times across all conversion ranges. Additionally, thermodynamic analyses indicated that Cu-SFO facilitated a more ordered and energetically favorable oxidation process, as demonstrated by increasingly negative entropy values and consistently lower Gibbs free energy. The research highlights the Cu-SFO catalyst exceptional ability to accelerate the transition from low-temperature to high-temperature oxidation while maintaining high catalytic activity. Taken together all these results, this research work contributes to provide comprehensive insights from the kinetic and thermodynamic analysis that reveal unique catalytic effects and reaction mechanisms, presenting an approach to stabilize combustion front and improve heavy oil recovery efficiency, addressing a critical challenge in the field of in-situ combustion.

The catalytic effect of Pt0 species on Pt/ZnO nanorods for robust triethylamine sensing detection

The noble metal Pt modified ZnO nanomaterials are widely used to improve their gas sensing performance. However, the relationship between the catalytic effect of Ptx+ species on the oxygen vacancies formation and gas-sensing performance is still unclear. Herein, the Pt/ZnO nanorods are successfully synthesized by using hydrothermal method, and the content of Pt0 species are finely tuned through treating in different atmospheres. Notably, Pt modified ZnO calcined under Ar/H2 (Pt/ZnO-3) exhibits excellent sensing response (Ra/Rg=2196, 81 times higher than pure ZnO) to 50 ppm triethylamine at 140°C, with fast response/recovery behavior, low limit of detection, and superior selectivity. Detailed structural characterization indicates that Pt nanoparticle modification reduces the band gap of the samples. In addition, the high content of Pt0 species promotes the generation of adsorbed oxygen, which significantly enhances the gas-sensitive performance of the sensor. This work demonstrates that the concentration of Pt0 species greatly affects gas-sensing performance.

Catalytic effect of the in-situ rhodium(III) complexes in surfactant medium on the auto-oxidation of 1,2-hydroxyphenylthiourea: A theoretical and experimental study for rhodium(III) sensing

1,2-hydroxyphenylthiourea(HPTU) undergoes auto-oxidation to form an yellow colored dimer. The process of auto-oxidation is enhanced by the presence of trace quantities of transition metal ions and transition metal complexes that act as catalysts. In the current study, catalytic potential of rhodium(III) complexes on the auto-oxidation of 1,2-hydroxyphenylthiourea(HPTU) was studied theoretically using quantum mechanical calculations and experiments were carried out using photometry and fluorometry. DFT studies inferred that [Rh(Py)6]Cl3 showed a better catalytic activity in the dimerization of HPTU. Theoretical studies were subsequently validated through experiments using photometric methods and the range of detection was determined to be 6 ng/mL–100 ng/mL. The detection limit was observed to be 2 ng/mL. Analytical parameters such as pH, reagent concentration, metal ion concentration, appropriate activators and surfactants were established.

Enhancing the dehydrogenation properties of LiAlH4 through the addition of ZrF4 for solid-state hydrogen storage

Hydrogen energy is emerging as an essential alternative to fossil fuels due to its clean energy profile, generating energy without greenhouse gas emissions. Solid-state hydrogen storage, particularly using complex hydrides like LiAlH4, holds promise due to high hydrogen capacities. However, practical applications of LiAlH4 face obstacles due to slow dehydrogenation kinetics and high decomposition temperatures. This study investigates the catalytic effect of ZrF4 on LiAlH4 to improve hydrogen storage properties. Incorporating 10wt.% ZrF4 has significantly lowered the onset desorption temperature from 160 °C to 80 °C. Desoption kinetic result showed that the addition of 10wt.% ZrF4 can enables the release of 5.6wt.% hydrogen in 120min at 100 °C, which is 50 times faster than in undoped samples. X-ray diffraction analysis indicated that ZrF4 facilitated the in-situ formation of Al3Zr and LiF phases during dehydrogenation, thereby enhancing catalytic efficiency. The desorption activation energies for first two reactions decreased significantly by ~ 16kJ/mol and ~24kJ/mol with ZrF4 doping. These findings suggest that ZrF4 effectively improves the hydrogen storage properties of LiAlH4, positioning it as a potential catalyst for solid-state hydrogen storage systems.

Ag-modified CuO-Fe2O3 composite catalysts for low-temperature NH3-SCO

A series of CuFe and Ag-modified CuFe composite catalysts were prepared for low-temperature selective catalytic oxidation of ammonia (NH3-SCO). Significant synergistic effects existed between Cu and Fe oxides in the CuFe(7:12) catalyst for catalyzing NH3 oxidation. Loading 6 wt.% Ag over CuFe(7:12) further enhanced NH3 conversion and N2 selectivity. At 200 °C, NH3 conversion and N2 selectivity reached 97.1 % and 79.3 %, respectively, over 6Ag/CuFe(7:12). Besides the exceptional catalytic effects of Ag species, the increased surface area, formation of CuFe2O4, improved reducibility of Cu and Fe oxides, and increased acid sites due to the composite of Cu and Fe and modification with Ag contributed to the superior performance of the 6Ag/CuFe(7:12) catalyst in NH3-SCO. In-situ DRIFTS results showed that NH3 oxidation might follow the internal selective catalytic reduction mechanism: NH3 was dehydrogenated and oxidized to NOx and nitrate species, and the formed NOx and nitrate species were reduced by the remaining NH3, −NH2 and −NH species to N2 and H2O. Loading Ag over CuFe(7:12) suppressed the formation of NO and NO2 but promoted that of N2O during NH3 oxidation, which could be attributed to the enhanced formation and decomposition of NH4NO3 in the presence of Ag.

Bright Nanocomposites based on Quantum Dot‐Initiated Photocatalysis

Integrating quantum dots (QDs) into polymer matrix to form nanocomposites without compromising the QD photoluminescence (PL) is crucial to emerging QD light‐emitting and solar energy conversion fields. However, the most widely‐used bulk polymerization technique, where monomers serve as the QD solvent, usually leads to QD PL quenching caused by radical initiators. Here we demonstrate high‐brightness nanocomposites with near‐unity PL quantum yield (QY), through a novel QDs‐catalyzed (‐initiated) bulk polymerization without using any radical initiators. Different from previous reports where QDs were designed as photo‐sensitizers/catalysts (always with cocatalysts) and hence non‐emissive in catalytic conditions, our QDs combine high brightness with highly effective catalysis, a combination that was previously considered to be hardly possible. In our case, apart from emitting light (at a large probability), the photoexcited QDs act as ‘overall reaction’ catalysts by simultaneously employing photoexcited electrons and holes to produce active radicals without the need of any sacrificial agents. These active radicals, though with a small amount, are sufficient to initiate effective chain reaction‐dominated bulk polymerization, eliminating the requirement of extra radical initiators. This study provides new insights for understanding and development of QDs for energy applications.

Bright Nanocomposites based on Quantum Dot-Initiated Photocatalysis.

Integrating quantum dots (QDs) into polymer matrix to form nanocomposites without compromising the QD photoluminescence (PL) is crucial to emerging QD light-emitting and solar energy conversion fields. However, the most widely-used bulk polymerization technique, where monomers serve as the QD solvent, usually leads to QD PL quenching caused by radical initiators. Here we demonstrate high-brightness nanocomposites with near-unity PL quantum yield (QY), through a novel QDs-catalyzed (-initiated) bulk polymerization without using any radical initiators. Different from previous reports where QDs were designed as photo-sensitizers/catalysts (always with cocatalysts) and hence non-emissive in catalytic conditions, our QDs combine high brightness with highly effective catalysis, a combination that was previously considered to be hardly possible. In our case, apart from emitting light (at a large probability), the photoexcited QDs act as 'overall reaction' catalysts by simultaneously employing photoexcited electrons and holes to produce active radicals without the need of any sacrificial agents. These active radicals, though with a small amount, are sufficient to initiate effective chain reaction-dominated bulk polymerization, eliminating the requirement of extra radical initiators. This study provides new insights for understanding and development of QDs for energy applications.

Formation and evolution of coke of pyrolytic volatiles of low-rank coal on the carbon-based catalysts

The catalytic upgrading of coal pyrolysis volatiles is an effective technique to achieve clean and efficient conversion of low-rank coal. However, a major problem in this process is catalyst deactivation caused by coke deposition. This study investigated the catalytic cracking effect of activated carbon and metal-modified activated carbon on coal pyrolysis volatiles. It also explained the physical and chemical properties of coke and its formation mechanism related to volatile cracking. The results indicate that phenolic oils, pitch, oxygen-containing compounds, and polycyclic aromatics are linearly related to the coke deposited on the surface of carbon-based catalysts. These compounds act as precursors and are easily transformed into coke via cracking, deoxidation, crosslinking, and polycondensation reactions when the cracking rate of volatiles does not match the hydrogen supply rate. The micro-morphology of coke is primarily composed of amorphous carbon, which is mainly found in pores ranging from 0.50 to 5.00 nm and on the outer surface of carbon-based catalysts. The chemical structure of coke primarily consists of large aromatic clusters containing at least six benzene rings and oxygen-containing cross-linking compounds with a high degree of graphitization and a low number of carbon structural defects. This results in an increase in radical concentration of carbon-based catalysts, as well as a decrease in combustion reactivity. The outcomes will aid in controlling coke deposition during catalytic cracking of pyrolytic volatiles of low-rank coal.

Enhanced Catalytic Activity for Production of Biodiesel from Aloe vera Oil and the Removal of Methyl Violet Dye using Polyaniline-Fe3O4 Magnetic Nanocomposite

The aim of this work was to use a unique technique to maximize the efficiency and cost-effectiveness of biodiesel synthesis utilizing Aloe vera oil. Moreover, in order to facilitate the magnetic separation from the resultant mixture, lipase was immobilized on a magnetic nanocomposite consisting of polyaniline (PANI) and Fe3O4. Utilizing XRD, SEM, TGA and FTIR spectroscopy, the nanocomposite was thoroughly characterized. The results indicated that the immobilized lipase exhibited enhanced thermal stability and a modified optimum pH compared to its free form. Using immobilized lipase also significantly improved the biodiesel conversion yield from 27% with free enzyme to 60%. Remarkably, after five cycles of reutilization in the production of biodiesel, the immobilized lipase retained 90% activity. The catalytic effectiveness of lipase during biodiesel synthesis was significantly enhanced and its resistance to heat and pH fluctuations was strengthened by this novel immobilization approach. Beyond its potential usage in biodiesel production, the PANI-Fe3O4 magnetic nanocomposite also demonstrated photocatalytic removal and degradation of methyl violet dye from aqueous solution.

Comparative Review for Enhancing CO2 Capture Efficiency with Mixed Amine Systems and Catalysts.

This study investigates methods to enhance the efficiency of CO2 capture using organic amine absorption and compares the performance of traditional and novel amine solvents. It reviews various single-component and mixed amine absorbents, as well as catalysts used in these methods, highlighting the superiority of mixed amine absorbents over single-component amine absorbents in CO2 absorption and desorption. Additionally, the study explores the catalytic mechanisms and effects of catalysts in the CO2 absorption/desorption process with amine solvents and provides an outlook on future research directions. The aim is to promote the widespread adoption of organic amine absorption technology in industrial applications and to contribute to the development of more sustainable and efficient CO2 capture technologies.

Intrinsic metal ion dual-regulated fabrication of multifunctional nano-interfacial BiFeVO4/Fe-MOF for high photo-Fenton-like synergistic catalytic oxytetracycline removal

Great disparity in crystal size and incompatibility in crystal interface of catalysts lead to low catalytic activity, restricting its application for antibiotic degradation. Herein, a dual regulation strategy via intrinsic ion interpenetration was proposed to engineer multifunctional nano-interfacial BiFeVO4/NH2-MIL-88B(Fe-Bi) (BFV/NMFB) catalysts for efficient photo-Fenton-like catalytic degradation OTC. These multifunctional nano-interfaces (Fe-O-Bi) with abundant vacancy defects enhanced electrical conductivity, broadened light absorption and narrowed band gap. Furthermore, the strong interface bonds enhanced H2O2 adsorption and activation, accelerated photogenerated carrier separation/transfer and promoted Fe3+/Fe2+ redox activity. These properties gave an excellent synergistic effect of photo and Fenton-like catalysis (synergy factor up to 4.6) via changing photocurrent transfer pathway and interfacial adsorption-activation mechanism. Therefore, the designed BFV/NMFB exhibited superior photo-Fenton-like catalytic activity (ka = 189 mol‧mg−1‧min−1), about 3.6–58 times higher than these of reported catalysts. The proposed strategy provided a promising method for the design of MOFs composition for application of antibiotic degradation.

Enhancing epoxy resin curing: Investigating the catalytic role of water as a trace impurity in dense crosslinked network formation using an advanced cat-GRRM/MC/MD Method1

The catalytic effect of water, a trace impurity in resins, facilitates efficient curing, affording a dense crosslinked network structure. Crosslinked networks are crucial for polymer properties. Water considerably influences the reaction pathways and kinetics and the final network structure and material properties. This study advances the cat-GRRM/MC/MD method to explore the specific role of water molecules as catalysts, though an impurity, in the curing of epoxy resins. Global reaction route mapping was used to compute the chemical reaction pathways and the corresponding energies. The resin properties were predicted via molecular dynamics simulations, complemented by the Monte Carlo method to simulate reaction kinetics and bond formation processes. Water molecules act as unique catalysts in the curing of epoxy resins, altering the reaction pathways and reducing the activation energies. The study revealed significant improvements in the physical properties of the resulting epoxy resins, aligning them more closely with the experimental material characteristics.

Macroscopic superlubricity achieved by hydrolysis reaction of ethyl lactate on silicon-doped diamond-like carbon film

Superlubricity between steel/diamond-like carbon (DLC) film could be achieved at vacuum or nitrogen condition, but it would be failed at ambient conditions. In this work, the macroscale superlubricity was achieved at ambient conditions by introducing ethyl lactate into ethylene glycol as lubricant additive for the friction pairs of silicon-doped diamond-like carbon (Si-DLC)/steel. Stable friction coefficient (μ = 0.002) and wear rate of friction pairs with the introduction of ethyl lactate could be respectively reduced by 99 % and 35 %. The characterization tests and density functional theory (DFT) calculation both demonstrated that the partial ethyl lactate was hydrolyzed into lactic acid due to the catalysis effect of steel surfaces. The molecular dynamics (MD) simulation result showed that the lactic acid molecules could be chemically adsorbed on the surfaces of friction pairs, forming a tribofilm through hydrogen bond with ethylene glycol molecules, which led to a significant reduction in the friction coefficient. This work presents a novel approach to achieve superlubricity on Si-DLC film with liquid, providing a great support for industrial application of superlubricity on DLC film.

Post-crosslinking knitting strategy for triazine-functionalized ionic hypercrosslinked polymers: Enhanced CO2 adsorption and conversion

Pore engineering has gained significant recognition as a pivotal strategy to tailor the structure and functionality of porous materials. In this study, a post-crosslinking knitting strategy was employed to fabricate a series of triazine-functionalized ionic hypercrosslinked polymers (IHCPs) using low specific surface area ionic polymers as precursors and external crosslinkers α,α′-dichloro-p-xylene (DCX) and α,α′-dibromo-p-xylene (DBX) through the Friedel Crafts alkylation reaction. This post-crosslinking knitting methodology increases the specific surface area of the resulting IHCPs, leading to enhanced CO2 adsorption capabilities (reaching 1.92 mmol·g−1 at 1 bar and 273 K), enhanced a remarkable 5.6-fold increase in CO2 uptake compared to the original ionic polymers. Of particular interest, inclusion of –NH– groups in PTA-2-DBX exhibits a synergistic catalytic effect facilitated by hydrogen bonding interactions that enable efficient conversion of CO2 into various cyclic carbonates under solvent- and cocatalyst-free conditions with yields exceeding 99 %. Furthermore, PTA-2-DBX demonstrates excellent recyclability while maintaining its activity even after five consecutive cycles. This study offers an effective approach for modulating pores in ionic polymers while highlighting the promising applications of triazine-functionalized IHCPs as dual-functional materials for both CO2 capture and conversion.

Tailoring iron hexadecafluorophthalocyanine/GO nanocomposite separators for polysulfide adsorption and enabling fast electrochemical kinetics of Li-S batteries

The cycling stability of lithium-sulfur batteries is significantly compromised by the shuttle effect. Herein, we employed a preformed process to successfully load spherical nanoparticles of Iron hexadecafluorophthalocyanine (FePcF16) with sizes between 10 and 20 nm onto oxidized graphene sheets. The FePcF16 spherical particles with lithium and sulfur-affinitive sites maximally expose catalytically active sites, facilitating effective adsorption and catalysis of polysulfides (LiPSs). Density-functional theory (DFT) calculations suggest that the electron-rich fluorine substituents enhance the conjugation effect of FePcF16, facilitating electronic communication between the catalyst and graphene oxide (GO), achieving precise modulation of the electronic structure of Fe-N4 active centers. The electrochemical analysis demonstrates that the nanostructured and Fe-N4 site-containing FePcF16 integrated with the robust two-dimensional graphene structure synergistically facilitates both redox reactions and lithium affinity effects. Consequently, in extended cycling tests at 2 C, the initial discharge-specific capacity reached 857.7 mAh g−1. After 500 cycles, the capacity remained at 737.7 mAh g−1, with a minimal capacity decay rate of only 0.028 % per cycle.

Assembly of artificial photo-enzyme coupling nanoreactor for boosting photodegradation of trace bisphenol A pollutant in water

It is a difficult issue to remove the trace persistent organic phenolic pollutants in water. Herein, a new artificial horseradish peroxidase (HRP)/hierarchical carbon nitride (HCN) photo-enzyme coupling nanoreactor is assembled by immobilizing HRP on HCN, which achieves the high-efficiency degradation performance for trace bisphenol A (BPA) in water. Besides the promoted charge separation efficiency as well as visible light harvest capacity, the hollow and abundant pores structure of HCN/HRP can provide a confinement effect and molecular diffusion channels to promote photo-enzyme synergic catalytic effect, thus boosting degradation reaction of BPA. Compared with original HCN, the optimal HCN/HRP-3 sample obtain a higher degradation rate of 0.0575 min−1, which is 3.60 and 125 times as large as that over original HCN (0.016 min−1) and HRP (0.00046 min−1), respectively. Meanwhile, the mineralization ability of the HCN/HRP photo-enzyme coupling nanoreactor is enhanced dramatically owing to the far higher TOC removal efficiency of BPA with 81.05 % within 60 min than original HCN (37.63 %). The photocatalytic reaction mechanism investigations demonstrate that h+, •O2− and •OH all take part in the degradation process of BPA and the importance order of h+ > •O2− > •OH. This work provides an innovative design philosophy for the assembly of photo-enzyme synergic catalytic system to effectively remove the organic pollutants in water.

Optimized Dehydrogenation of Magnesium Hydride with Fe and Cu Additives

Solid state hydrogen storage with the use of MgH2 has gained widespread attention because of its good reversible storage capacity. This metal hydride however slowly releases hydrogen at high temperatures ranging between 325 – 375 oC. An important feature required of MgH2 is its ability to commence hydrogen release at a fast rate and reduced temperature. Transition metal-containing alloys/compounds having either Fe or Cu as the principal element have been used to improve the dissociation of hydrogen from MgH2. Studies involving the use of each metal in its elemental form as an additive are minimal. This study investigated the catalytic effects of elemental Fe and Cu on the hydrogen release performance of MgH2 for potential applications in transportation and power generation. It was observed that MgH2/Fe had a better dehydrogenation performance; the temperature of onset of MgH2/Fe and MgH2/Cu dehydrogenation were 205, and 215 oC which were 98 and 88 oC lower than that for as-received MgH2. The highest amount, 1.9 wt. % H2 was released by MgH2/Fe while 1.44 wt. % H2 was released by MgH2/Cu. The activation energy for dehydrogenation was reduced from 150.5 kJ/mol for as-received MgH2 to 89.8 and 79.8 kJ/mol in MgH2/Cu and MgH2/Fe respectively. It took 18.8 min for as-received MgH2 to commence dehydrogenation while that for MgH2/Fe and MgH2/Cu composites started from 12.2 and 13.4 min respectively. The in-situ formed Fe and Cu in MgH2 after milling acted as active catalytic sites for its improved dehydrogenation with MgH2/Fe behaving better.

Evaluating the Ability of External Electric Fields to Accelerate Reactions in Solution.

This study investigates the catalytic effects of external electric fields (EEFs) on two reactions in solution: the Menshutkin reaction and the Chapman rearrangement. Utilizing a scanning tunneling microscope-based break-junction (STM-BJ) setup and monitoring reaction rates through high-performance liquid chromatography connected to a UV detector (HPLC-UV) and ultraperformance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-q-ToF-MS), we observed no rate enhancement for either reaction under ambient conditions. Density functional theory (DFT) calculations indicate that electric field-induced changes in reactant orientation and the minimization of activation energy are crucial factors in determining the efficacy of EEF-driven catalysis. Our findings suggest that the current experimental setups and field strengths are insufficient to catalyze these reactions, underscoring the importance of these criteria in assessing the reaction candidates.

High-performance ammonium perchlorate propellants enabled by ferrocene-functionalized carbon nanotube catalysts

Ferrocene-based burning rate catalysts (BRCs) are essential for controlling the combustion of ammonium perchlorate (AP)-based composite solid propellants. However, their efficacy is often limited by migration during storage, leading to performance degradation. This work reports a novel class of covalently grafted ferrocene-functionalized multi-walled carbon nanotubes (CNT-Fc-n, n = 1, 2, 3) exhibiting enhanced catalytic activity and anti-migration properties. Structural characterization confirmed successful functionalization, while electrochemical analysis revealed facilitated electron transfer during AP decomposition due to π-π conjugation within the CNT-Fc-n structure. Consequently, CNT-Fc-n catalysts significantly reduced the AP decomposition activation energy, with CNT-Fc-3 (highest ferrocene loading) demonstrating the most pronounced catalytic effect. Specifically, CNT-Fc-3 lowered the AP decomposition temperature by 103 °C and 39 °C compared to pure AP and Catocene-catalyzed AP, respectively. Kinetic analysis revealed a 28-fold increase in the rate constant for CNT-Fc-3 catalyzed AP decomposition compared to pure AP. Moreover, the unique architecture of CNT-Fc-3 significantly reduced migration during a 50 °C simulation. This work presents a promising strategy for developing high-performance, migration-resistant BRCs for next-generation solid propellants.