Preparation Of Catalysts Research Articles

Triggered Directed Electron Redistribution Endowed by Efficient Ohmic Contacts of NiMoN/Ni3S2 for Boosting Large Current‐Density Overall Seawater Splitting

AbstractThe rational construction of interfacial nanostructures of metal/semiconductor (MS) contacted electrocatalysts has a significant impact on improving their intrinsic activities. However, MS contacts are often plagued by a strong Fermi‐level pinning effect, resulting in the formation of the Schottky barrier that affects the adsorption of hydrogen/oxygen intermediates. Herein, an Ohmic contact between metallic Ni3S2 and semiconducting NiMoN is well‐designed, which effectively reduces the electron conduction barriers. The as‐obtained NiMoN/Ni3S2 has remarkable bifunctional water electrolysis performance. At 10 mA·cm−2, the overpotential of hydrogen evolution and oxygen evolution reaction is 70 and 154 mV, respectively. Impressively, the formation of hydroxide during surface reconstruction can avoid the chlorine evolution on the catalyst surface. At an industrial process temperature of 85 °C, it takes only 340 mV for the overall seawater splitting of 500 mA·cm−2. UPS and UV‐VIS diffuse spectra combined with theoretical calculation results confirm that the self‐driven directed electron transfer derived from the Ohmic contact can induce local electron enrichment at the interface region, thus promoting the formation of *O to *OOH. This study provides important insights into the coordinated modulation of built‐in electric fields and the preparation of efficient multifunctional catalysts with a high abundance of active sites.

Construction of bicarbonate-porous poly(ionic liquid)s for cycloaddition of CO2 and epoxides under mild conditions

The utilization of carbon dioxide (CO2) as a C1 building block to synthesize cyclic carbonates represents an environmentally and sustainably viable approach. Nevertheless, the preparation of metal- and halogen-free porous materials remains a promising avenue for the cycloaddition reaction. In this context, we have designed a bicarbonate-porous poly(ionic liquid)s (PEI/PS-HCO3) catalyst with a mesoporous structure for the construction of multiple active sites through quaterisation and ion exchange. The as-prepared PEI/PS-HCO3 catalyst exhibited excellent catalytic activity for the synthesis of cyclic carbonates, with yields of up to 93% under metal-, solvent- and halogen-free conditions. Furthermore, the catalyst exhibited excellent reusability by washing with anhydrous ethanol. The feasible reaction mechanism was proposed. The interaction of dual hydrogen bond donors (amine groups and [HCO3]− anion) with epichlorohydrin (ECH) via hydrogen bonding results in the polarisation of the epoxide C-O bond. Amine groups, also acting as Lewis base sites, captured CO₂ to produce carbamates ([NH-COO]−). The nucleophilic [HCO3]− attacked the less sterically hindered β-carbon atom of epichlorohydrin (ECH). This protocol provides a novel strategy for the preparation of halogen-free catalysts.

Highly valent cobalt-manganese spinel nanowires induced by fluorine-doping for durable acid oxygen evolution reaction

The increase in the fraction of high-valent metal cations is of significant importance for enhancing the stability of noble-metal-free catalysts in the acid oxygen evolution reaction (OER). Herein, we report the preparation of a cobalt-manganese oxide spinel nanowire catalyst, where the incorporation and stabilization of high-valent cation fractions are induced by electron-withdrawing anionic fluorine groups. By the XPS, the strongly electronegative F atoms improve the ratio of Co3+/Co2+ and Mn4+/Mn3+, thereby enhancing OER activity and stability. The hydrophilicity F-MCO nanowires have a large specific surface area and great conductivity, which expose more catalytically active sites and continuously promotes oxygen evolution. The proposed F-MCO catalyst requires only an overpotential of 210 mV at the current density of 10 mA cm−2 and can maintain stable operation for more than 100 h. And a photovoltaic-electrolysis device with the F-MCO electrocatalyst delivers a solar-to-hydrogen efficiency of 15.1 %.

Selective reduction of CO2 to CO over alumina-supported catalysts of group 5 transition metal carbides

We show the applicability of a preparation method, previously reported for obtaining tailored bulk VCx catalysts, for alumina-supported G5TMCs. The characteristics of the G5TMCs/Al2O3 catalysts and their behaviour in the selective reduction of CO2 to CO through the RWGS reaction is reported. VCx/Al2O3 catalysts were active, stable and highly selective; meanwhile NbC/Al2O3 and TaC/Al2O3 were not active. VCx/Al2O3 catalysts exhibited selectivity to CO over 99.5 % at temperature above 773 K. The characteristics of alumina-supported vanadium carbide particles depended on the vanadium precursor and on the atmosphere used during the catalyst preparation. XPS characterization of VCx/Al2O3 catalysts revealed the presence of carbide species on surface before and after RWGS reaction. The catalytic behaviour of VCx/Al2O3 is analysed in the light of their characteristics and compared with bulk VCx counterparts. The most performant catalyst, VC(Pr)/Al2O3, was stable over 4 days at 723 K, with ∼100 % selectivity to CO and CO2 conversion of ∼11 %.

Effect of A-site cation doping on the catalytic oxidation of toluene over mullite catalyst GdMn2O5

Manganese-based mullite (AMn2O5) catalysts are promising for the catalytic oxidation of VOCs, with their oxidation reaction performance being tunable by modifying the composition of the A-site elements. In this work, various manganese-based mullite catalysts (Gd0.9X0.1Mn2O5, X =Sr, Ce, or Ca) with different A-site elements doping were prepared by the citric acid sol–gel method and applied to the catalytic oxidation of toluene. The activity tests indicated that the enhancement of catalytic performance by doping elements was in the order of Sr > Ce > Ca. Notably, the T90 of the Gd0.9Sr0.1Mn2O5 catalyst was 235.6 °C, a lower 37.8 °C than that of the GdMn2O5. Comprehensive characterization and density functional theory (DFT) simulations revealed that Sr doping facilitates the reduction of Mn4+ to Mn3+, increases the electron occupancy of the eg orbitals in octahedral Mn sites, and elevates the Mn-d band center, thus facilitating the adsorption and activation of O2. Additionally, the raised O-p band center caused by Sr doping enhances lattice oxygen mobility. In situ DRIFTS analysis indicated that the introduction of Sr at the A-site optimizes the toluene reaction pathway and accelerates the reaction rate. This work reveals that a simple A-site cation doping strategy can effectively regulate manganese-based mullite catalysts’ electronic structure and surface reaction activity, providing a feasible method for the large-scale preparation of manganese-based mullite catalysts with excellent catalytic performance.

Peroxymonosulfate activation by CoO@C catalyst from integrated recycling of spent lithium-ion battery: Performance and mechanism

Developing low-cost, highly active transition metal-based catalysts for peroxymonosulfate (PMS) activation is essential but remains challenging. Herein, we proposed a novel “waste-to-energy” strategy to derive an effective PMS activator (CoO@C) by integrally utilizing the abundant Co content in the cathodes and the defective structure of anode graphite from spent lithium-ion batteries (LIBs). The CoO@C/PMS system could completely degrade atrazine (ATZ) within 15 min, along with a robust resilience to coexisting substrate and a wide pH range of 5.0–11.0. Through quenching experiments and electron paramagnetic resonance (EPR), •OH was identified as the primary reactive oxygen species (ROS) responsible for ATZ degradation. Furthermore, electron transfer between the catalyst and PMS was examined via density functional theory (DFT) calculations to elucidate the activation mechanism. The Fukui index pinpointed the vulnerable sites of ATZ, offering insights into the possible degradation pathways along with UHPLC-MS analysis. Furthermore, CoO@C was fixed on a polyethersulfone (PES) membrane for continuous degradation of ATZ, which maintained a degradation efficiency exceeding 90 % after treating 6 L of wastewater. This research provided valuable insights into the preparation of metal-based catalysts for advanced oxidation processes and achieved the sustainable utilization of spent LIBs.

Rapid removal and catalytic decomposition of nitrate in anion-exchange resin containing gold nanoparticles toward purification of groundwater

We investigated the catalytic reduction of NO3– in various single-metal-introduced anion-exchange resins (AERs) in 1 bar H2 and observed that the reaction proceeded successfully. Among the metals considered in this study, Au was optimal in terms of catalytic activity and ease of catalyst preparation, whereas Ru exhibited the highest activity. The AER with Au (Au@AER) containing the optimal amount of Au (0.3mmol/g) decomposed 0.38mmol/g of NO3– primarily into N2O under optimized reaction conditions (80°C and 5 h). The decomposition amount corresponded to 41 % conversion. The incorporation of Au into the AER increased its ion-exchange capacity from 1.18 (pristine AER) to 1.46mmol/g (Au@AER); in contrast, the ion-exchange equilibrium constant decreased from 1.4 to 0.83 L mol−1 owing to the change in the structure of the anion-exchange sites in the AER. Au@AER was reusable for ion-exchange removal and catalytic decomposition of NO3– up to five times without performance degradation.

Efficient palladium ion adsorption and catalyst preparation from pharmaceutical wastewater using amino-functionalized Ti3C2

This paper reports the recovery and reuse of Pd ions from pharmaceutical wastewater using amino-modified Ti3C2. Ti3C2–NH2 was synthesized by modifying (3-aminopropyl)triethoxysilane and the successful substitution of some surface functional groups of Ti3C2; the decrease in material thickness was verified by characterization. This study revealed that the presence of amino groups significantly enhanced the Pd(II) adsorption capacity of Ti3C2. The effects of the adsorbent material, adsorbent dosage, pH, initial concentration of Pd ions, presence of competing cations, and contact time on the adsorption performance were investigated. The maximum adsorption capacity of 20 mg of Ti3C2–NH2 was 986.65 mg/g in 100 ml of a Pd-ion solution with an initial concentration of 200 mg/l at pH 3. A pseudo-second-order kinetic model fitted well with the experimentally obtained rate data, indicating that the main mode of Pd-ion removal by Ti3C2–NH2 was via chemical reduction. Finally, the catalyst exhibited excellent performances during the photocatalytic and Suzuki coupling reactions with yields of 81 % and 95 %, respectively. The results demonstrated that Ti3C2–NH2 is an excellent material for adsorbing Pd ions and can effectively recycle these ions from pharmaceutical wastewater.

Metal‐Supported Heterogeneous Catalysts for the Synthesis of Nitrogen‐Containing Heterocycles: A Comprehensive Review

AbstractThe use of metals in the preparation of heterocycles has become increasingly popular due to several key advantages of metals as catalysts. These include recycling capability, eco‐friendliness, simplicity of catalyst preparation and separation, longer lifespan, abundance, and higher yields. As a result of their novel applications in organic, inorganic, medicinal, industrial, polymer chemistry, material sciences, nanotechnology, and biological processes, the utilization of nitrogen‐containing heterocycles has rapidly increased in recent years. Various nitrogen‐containing organic moieties are used in therapeutic processes to enhance effectiveness against several bacterial and viral diseases. This review covers the preparation of imidazoles, triazoles, tetrazoles, pyridine derivatives, azo compounds, pyrimidines, quinoxalines, and quinolines using metals as heterogeneous catalysts. It provides an overview of current methodologies for metal‐assisted heterogeneous catalytic reactions, including product yield, operating temperature, and solvents, among other factors. Heterogeneous catalyst‐mediated organic synthetic reactions offer several advantages, particularly in medicinal chemistry, pharmaceuticals, and industrial applications, by reducing time and energy consumption. This review emphasizes recent advancements in the fabrication of nitrogen heterocycles utilizing heterogeneous catalysts, taking into account various economic, eco‐friendly, and user‐friendly considerations. Additionally, it discusses the benefits, reaction conditions, and yields reported in the literature over the past six years.

Effective hydrogen production and coupling degradation of organics (4-nitrophenol, methylene blue, and Rhodamine B) in wastewater by electrospun PAN@Fe0 composite nanofibers

The pursuit of clean energy generation and environmental preservation is of utmost importance for societal progress. However, couple clean energy production and pollution control is still a difficulty. In this study, a novel electrospun composite mat, with nano zero valent iron (Fe0, nZVI) encapsulated into polyacrylonitrile (PAN) nanofibers was acted as a catalyst. The activation energy (Ea) for the hydrolysis of NaBH4 to produce hydrogen is 22 kJ·mol−1, hydrogen atom utilization efficiency (HGE) of NaBH4 is 60.80%. Three kinds of organic dyes 4-nitrophenol (4-NP), methylene blue (MB), and Rhodamine B (RhB) were served as the model pollutant, to construct NaBH4-organic system for energy production and pollution reduction. The NaBH4-organic system demonstrates a collaborative capability to simultaneously remove organic pollutants and generate hydrogen, with a coupling equilibrium point between the two processes. The hydrogen generation rate (HGR) and HGE increased with the concentration of pollutants increased. The degradation of 4-NP, MB, and RhB followed pseudo-first-order kinetics, with RhB degrading dosage 20 and 44 times higher than 4-NP and MB, respectively. H2 and H· contributed to the organic degradation. nZVI directly participated in the formation H2 and H·. PAN@Fe0 possessed good recyclability and moderate cost. The degradation process adhered to the classical surface reaction controlled Langmuir-Hinshelwood (L-H) model. The integration of synergistic production capacity and pollutant degradation aligns well with the principles of green chemistry and sustainable development. This study demonstrates a novel approach to no precursor loss catalysts preparation, efficient production clean H2, advanced treatment of dye-containing wastewater, carbon neutral operation of sewage treatment plant.

Water-retaining slurry washcoat for high-loading and robust CuMnOx structured catalyst toward durable monoxide oxide purification from real flue gas

Structured catalysts play key roles in many industries with the advantages of low pressure drop and efficient mass transfer. The copper-manganese oxide (CuMnOx) as a cost-effective catalyst has been widely applied in gas purification, but still lack efficient structured catalyst due to the challenge in controlling its slurry and coating quality. In this work, this challenge was addressed by introducing the water-retaining agent (WRA) into slurry with sophisticatedly designed conditions. The effects of the type and dosage of WRA, pH value, and temperature on slurry properties including viscosity, stability, and water-retention were systematically studied, and the slurry property-coating quality relationship was correlated. The preferred slurry and coated layer could be segregated into sub-millimeter-sized water-retaining regions where catalyst and binder particles were well dispersed and connected. After slow release of water and organic during drying and calcination, the CuMnOx structured catalyst with uniform, defect-free and dense coating was obtained, showing high loading (>160 kg/m3), great mechanical strength (powder shedding rate < 1 wt%), and no blockage for practical use. The robustness of the structured catalysts was validated by a scale-up preparation of 2 m3 volume amount for CO purification from real ore-sintering flue gas in a steel plant, which achieved the CO catalytic efficiency maintaining over 90 % for more than 1440 h. This work showcases an efficient strategy for structured catalyst preparation and expands the gas purification application of the industrially-favored CuMnOx.

Cross-Linked Polyvinylimidazole Complexed with Heteropolyacid Clusters for Deep Oxidative Desulfurization.

The combustion of fuel with high sulfur concentrations produces a large number of sulfur oxides (SOx), which have a range of negative effects on human health and life. The preparation of catalysts with excellent performance in the oxidative desulfurization (ODS) process is highly effective for reducing SOx production. In this paper, cross-linked polyvinylimidazole (VE) was successfully created using a simple ontology aggregation method, after which a catalyst of polyvinylimidazolyl heteropolyacid clusters (VE-HPA) was prepared by adding heteropolyacid clusters. Polyvinylimidazolyl-phosphotungstic acid (VE-HPW) showed an outstanding desulfurization performance, and the desulfurization efficiency reached 99.68% in 60 min at 50 °C with H2O2 as an oxidant. Additionally, the catalyst exhibited recyclability nine consecutive times and remained stable, with a removal rate of 98.60%. The reaction mechanism was eventually proposed with the assistance of the free radical capture experiment and GC-MS analysis.

In-situ growth strategy to synthesize porous nano-coral-like structure OER catalyst based on nife foam alloy substrate

The preparation of alloy-based catalysts is an effective approach to simplify the catalyst synthesis process for electrocatalysis. The oxygen evolution reaction (OER) is considered a key step in water splitting. By incorporating interface engineering design, electronic state optimization, and heteroatom doping, the electrocatalytic performance can be enhanced. In this study, a simple method was used to activate the NiFe foam (NIF) alloy substrate by acid etching, followed by in-situ S-doping of Cr via a hydrothermal method to synthesize S-Cr0.6@NiFe/NIF catalyst material. Its outstanding porous nanocoral-like structure not only provides abundant active sites but also exhibits superior catalytic water splitting performance, demonstrating superhydrophilic and superaerophobic characteristics. At a current density of 10 mA cm−2, only 262 mV overpotential is required to drive the OER (under basic conditions of 1 M KOH), with a low Tafel slope (71.6 mV dec−1) and a large electrochemical active surface area (ECSA = 85.25 cm2). After 80 hours of OER test, the current density of S-Cr0.6@NiFe/NIF shows negligible change. This study provides an attractive, effective, and feasible method for the in-situ growth design of alloy-based catalysts.

Bifunctional 0D carbon quantum dot cathode electrocatalyst coupled with atomic hydrogen and hydroxyl radicals for efficient removal of oxytetracycline hydrochloride

Efficient removal of antibiotics is difficult to achieve by conventional single-oxidation or reduction processes. Herein, a bifunctional cathodic electrocatalyst coupling atomic hydrogen (H*) reduction with hydroxyl radical (·OH) oxidation in an efficient electrocatalytic process was developed for the effective degradation of oxytetracycline hydrochloride (OTC). Pd particles were dispersed on B-doped carbon quantum dots to prepare a Pd-B-doped carbon quantum dots/titanium (Pd-BCQD/Ti) electrode as a bifunctional cathode catalyst. The electrode can simultaneously generate H* through the H2O/H+ reduction process, H2O2 through the oxygen reduction process, and then generate ·OH. H* performs nucleophilic hydrogenation reduction of OTC molecules, and ·OH performs electrophilic oxidation of the carbon skeleton, and both act synergistically with the active chlorine species (HClO) generated at the anode. The experimental results showed that the electrode achieved 90.50 % removal of OTC within 60 min. In addition, the Pd-BCQD/Ti electrode reduces energy consumption while increasing current efficiency. The degradation effect was more than 85.80 % in the pH range of 3∼9, indicating fairly stable catalytic activity over a wide pH range. The degradation efficiency was basically unchanged after ten cycles, and the reactivity was still high in the actual water. Intermediates were analyzed based on LC-MS to explore the degradation pathways of OTC. The toxicity of the intermediates generated during OTC degradation was predicted based on quantitative conformational relationships. This study provides a feasible strategy for the preparation of bifunctional catalysts based on zero-dimensional BCQD for efficient green antibiotic wastewater treatment.

Calcium single atoms stabilized by nitrogen coordination in metal–organic frameworks as efficient solid base catalysts

Considerable attention has been paid to the preparation of single-atom solid base catalysts (SASBCs) owing to their high activity and maximized utilization of basic sites. At present, the reported fabrication methods of SASBCs, such as two-step reduction strategy and sublimation capture strategy, require high temperature. Such a high activation temperature is easy to cause the sublimation loss of alkali or alkaline earth metal atoms and destructive to the support structure. Herein, a new SASBC, Ca1/UiO-67-BPY, is fabricated, in which the alkaline earth metal Ca sites are immobilized onto N-rich metal–organic framework UiO-67-BPY at room temperature. The results show that the atomic configuration of Ca single atoms is coordinated by two N atoms in the framework. The obtained Ca SASBC possesses ordered structure and exhibits high product yield of 87.2% in the Knoevenagel reaction between benzaldehyde and malononitrile. Furthermore, thanks to the Ca single atoms sites anchored on UiO-67-BPY, the Ca1/UiO-67-BPY catalyst also shows good stability during cycles. This work might offer new insight in designing SASBCs for different base-catalyzed reactions.

Facile and scalable synthesis of N-doped carbon based Ni electrocatalyst for efficient CO2 reduction to CO

Electrochemical reduction of CO2 into valuable chemical products could be realized by reasonable design of effective electrocatalysts with atomically dispersed active sites, but the task presents challenges for chemistry because of the lack of facile and scalable synthetic route. Therefore nitrogen-doped porous carbon supported Ni electrocatalyst is presented via a facile synthetic method. In the first step, commercial carbon black was oxidized by HNO3 to generate organic group followed by absorption of Ni ions. Secondly, calcination under NH3 atmosphere led to N doped carbon based Ni catalyst which exhibited excellent catalytic performance with approximate 95 % Faradaic efficiency for CO, which is helpful for chemists to reasonable design and scalable preparation of economical and efficient catalysts.

Electrodeposited Pt nanoparticles loaded on support composites of metal-organic frameworks and carbon quantum dots for the enhancement of alcohol electrooxidation

Metal-organic frameworks comprising divalent metal (M)-linked 4,4′-bipyridine (bpy), {[CuII4(bpy)3(OH)2(mal)3]·4H2O}n(Cubpy) and Ni2(bpy)3(NO3)4(H2O)4(Nibpy) were modified with carbon quantum dots (Mbpy/CQD; M = Cu, Ni) to prepare a composite support. Then, platinum (Pt) nanoparticles were electrodeposited onto the modified Mbpy/CQD support for the preparation of Pt-based catalysts (Pt/Mbpy/CQD) for the electrocatalytic improvement of alcohol oxidation. The influence of Mbpy with electrodeposited Pt nanostructures on CQD support electrodes is particularly discussed in detail through numerous physical characterizations, e.g., SEM, TEM, EDX, XPS, XRD, and elemental mapping. Dispersed Pt nanoparticles with diameters of 3-10 nm can be obtained on the modified Mbpy/CQD supports with suitable chemical and structural conditions for electrocatalytic oxidation improvement. The various prepared Pt/Mbpy/CQD catalysts with different compositions also enhance the kinetics of alcohol oxidation; they have a greater electrochemically active surface area (ECSA) and more development activity for alcohol oxidation than do the Pt/CQD catalysts. For the oxidation of all the selected small alcohol molecules, e.g., methanol, ethanol and isopropanol, the Pt/Cubpy/CQD catalyst composites also mostly exhibited improved catalytic activity, outstanding stability, and lower onset potential (Eonset) and CO tolerance. The favorable performance of the prepared composite catalysts is attributed to their superior ECSA owing to the suitable mixed surface of metal and functional groups of electrodeposited Pt, Mbpy, and CQD on the catalytic composites. Consequently, these as-prepared Pt/Mbpy/CQD composites, which are promising oxidative heterogeneous catalysts, can be used as active and stable catalysts for alcohol oxidation in alkaline solutions.

Regulating oxidation states of Cu nanowires for enhanced catalytic reduction of 4-nitrophenol

Abstract The construction of highly efficient and low-cost catalysts is crucial for the reduction reaction of 4-nitrophenol (4-NP). Herein, we provide a simple processing method, including vacuum storage, natural oxidation, and heating oxidation, that effectively regulates the surface oxidation state of copper nanowires and produces copper nanowires with different oxidation states (such as Cu, Cu2O, and CuO). Research has found that CuNW-N (Cu nanowires for vacuum storage) catalysts with a surface composition of 67.9% Cu0, 20.6% Cu+, and 11.5% Cu2+ exhibit the best catalytic performance for the reduction of 4-nitrophenol (4-NP) and their reaction rate constant reaches 0.791 min−1. This work provides a feasible catalyst preparation strategy for the efficient catalytic reduction of 4-NP.

Preparation of silicon foam supported CoMn catalysts and their catalytic performances in higher alcohol synthesis via syngas

A series of silicon foam supported CoMn catalysts were prepared using impregnation, precipitation, and hydrothermal methods. Combining the characterization techniques such as XRD, H2-TPR, N2 physical adsorption, TEM, and XPS, the effect of different catalyst preparation methods on the catalytic performance in the synthesis of higher alcohols from syngas was investigated. It is shown that there are Co2+(Co2C) and Co0 species on the surface of the catalyst. The active sites of Co2C-Co0 on the surface of the catalyst prepared by hydrothermal method have a good synergistic effect, which is conducive to the generation of alcohols. A higher proportion of Co2C also promotes the associative adsorption and insertion of CO, resulting in the highest alcohol selectivity. Under the reaction conditions of t=260 °C, p=5.0 MPa, GHSV=4500 h–1 and H2/CO(volume ratio)=2:1, the catalyst exhibited the best reaction performances with CO conversion of 11.1%, total alcohol selectivity of 34.7%, and C2+OH selectivity of 34.5%.

Preparation of Pt-Based Bimetallic Catalysts and Electrocatalytic Performance for Methanol Oxidation

Preparation of Pt-Based Bimetallic Catalysts and Electrocatalytic Performance for Methanol Oxidation