As-synthesized Catalysts Research Articles

Interface engineering of BiVO4/Zn3V2O8 heterocatalysts for escalating the synergism: Impact of Cu electron mediator for overall water splitting

The risk of global warming is increasing due to excessive consumption of fossil fuels. To fill the gap between production and consumption of conventional energy sources, modern societies are searching green and renewable alternatives. In this work, BiVO4/Zn3V2O8 heterocatalysts were synthesized and interfacially engineered for overall water splitting reactions. To obtain the structural and interfacial morphologies, catalysts were characterized by XRD, FTIR, Raman spectroscopy, SEM and AFM techniques. The optical and chemical characteristics of as-synthesized catalysts were evaluated using UV–Vis/DRS, PL, EIS, EDX, XPS and BET analysis. The role of Cu metal, synergism between BiVO4/Zn3V2O8 and mechanistic approaches were further revealed. The results depict that Cu metal exceptionally compete to sustain the synergism as an electron mediator source. The synergistic effect and electron mediator were found as key factors to boost the overall water splitting efficiencies. Due to interfacial engineering of BiVO4/Zn3V2O8 system, charge transfer becomes more feasible for the redox reactions (i.e. water splitting). It was examined that due to presence of Cu metal, rate of overall water splitting reaction was higher than the catalysts having no mediator (i.e. absence of Cu). During photoreaction, two successive rates for H2 and O2 evolution were speculated 17.66 and 8.96 mmol g−1 h−1, respectively which delivers approximately 5.04 kJ g−1 h−1 energy. On the basis of results and activities, it could be concluded that, this research will exhibit exceptional potential and hold promise of an ultimate transition to the water splitting and green energy technologies.

Harnessing bimetallic oxide nanoparticles on ionic liquid functionalized silica for enhanced catalytic performance

The present study reports on harnessing bimetallic (V and Ni) oxide nanoparticles supported on ionic liquid-functionalized silica for enhancing catalytic performance in epoxidation and hydrogenation reactions. The as-synthesized catalyst was ably characterized through various techniques such as FTIR, X-ray diffraction (XRD), N2 adsorption−desorption isotherms, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). A selective organic transformation of Isophorone to Homalinol via two-steps tandem reaction significantly promoted by synthesized catalyst. During epoxidation and hydrogenation reactions, V-NiNPs@SILP catalyst demonstrated excellent catalytic performance, leading to 98.23 % conversion with 99.06 % selectivity. Moreover, the synthesized catalyst exhibited recyclability for five consecutive cycles with minute loss in activity.

Cu-Modified Palladium Catalysts: Boosting Formate Electrooxidation via Interfacially OHad-Driven Had Removal.

Direct formate fuel cells have gained traction due to their eco-friendly credentials and inherent safety. However, their potential is hampered by the kinetic challenges of the formate oxidation reaction (FOR) on Pd-based catalysts, chiefly due to the unfavorable adsorption of hydrogen species (Had). These species clog the active sites, hindering efficient catalysis. Here, we introduce a straightforward strategy to remedy this bottleneck by incorporating Pd with Cu to expedite the removal of Pd-Had in alkaline media. Notably, Cu plays a pivotal role in bolstering the concentration of hydroxyl adsorbates (OHad) on the surface of catalyst. These OHad species can react with Had, effectively unblocking the active sites for FOR. The as-synthesized catalyst of PdCu/C exhibits a superior FOR performance, boasting a remarkable mass activity of 3.62 A mg-1. Through CO-stripping voltammetry, we discern that the presence of Cu in Pd markedly speeds up the formation of adsorbed hydroxyl species (OHad) at diminished potentials. This, in turn, aids the oxidative removal of Pd-Had, leveraging a synergistic mechanism during FOR. Density functional theory computations further reveal intensified interactions between adsorbed oxygen species and intermediates, underscoring that the Cu-Pd interface exhibits greater oxyphilicity compared to pristine Pd. In this study, we present both experimental and theoretical corroborations, unequivocally highlighting that the integrated copper species markedly amplify the generation of OHad, ensuring efficient removal of Had. This work paves the way, shedding light on the strategic design of high-performing FOR catalysts.

A novel bimetallic CaFe-MOF derivative for transesterification: Catalytic performance, characterization, and stability

Metal organic frameworks (MOFs) are ideal precursors for the synthesis of catalysts with high surface areas and homogenously distributed active sites. Compared to monometallic MOFs, MOF-on-MOF strategy shows enhanced properties originating from the synergistic interactions between two metals at atomic level. In this study, a bimetallic CaFe-MOF was synthesized and exploited to obtain magnetic CaO catalyst, which was subsequently applied to catalyze transesterification for biodiesel production. The catalysts were characterized with thermogravimetric/derivative thermogravimetric analysis (TG/DTG), X-ray diffraction (XRD), Fourier Transform Infrared spectrometer (FTIR), N2 adsorption-desorption, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), and Hammett indicator method. The as-synthesized catalysts exhibit excellent catalytic activity of 98.53 % with 6 wt% catalyst amount and 12 methanol/oil molar ratio at 65 °C in 1 h. The synthesized catalyst showed good stability even after 6 recycles with favorable transesterification conversions. Moreover, the as-synthesized catalyst type is highly tolerant to free fatty acid (FFA) and free water (FW), with transesterification conversions of 85.35 % and 86.27 % achieved with the FFA of 9 wt% and FW of 11 wt%, respectively. The physicochemical properties of the obtained biodiesel meet requirements of ASTM D6751 and EN 14214, indicating it can be directly used for transport fuel.

Phytoassisted synthesis of CuO and Ag–CuO nanocomposite, characterization, chemical sensing of ammonia, degradation of methylene blue

The elimination of hazardous industrial pollutants from aqueous solutions is an emerging area of scientific research and a worldwide problem. An efficient catalyst, Ag–CuO was synthesized for the degradation of methylene blue, the chemical sensing of ammonia. A simple novel synthetic method was reported in which new plant material Capparis decidua was used for the reduction and stabilization of the synthesized nanocatalyst. A Varying amount of Ag was doped into CuO to optimize the best catalyst that met the required objectives. Through this, the Ag–CuO nanocomposite was characterized by XRD, SEM, HR-TEM, EDX, and FTIR techniques. The mechanism of increased catalytic activity with Ag doping involves the formation of charge sink and suppression of drop back probability of charge from conduction to valance band. Herein, 2.7 mol % Ag–CuO exhibited better catalytic activities and it was used through subsequent catalytic experiments. The experimental conditions such as pH, catalyst dose, analyte initial concentration, and contact time were optimized. The as-synthesized nanocomposite demonstrates an excellent degradation efficacy of MB which is 97% at pH 9. More interestingly, the as-synthesized catalyst was successfully applied for the chemical sensing of ammonia even at very low concentrations. The lower limit of detection (LLOD) also called analytic sensitivity was calculated for ammonia sensing and found to be 1.37 ppm.

Rationally designed CeO2 decorated Ti3C2 MXene interface for efficient water splitting and enhanced supercapacitor performance

MXenes serve as competent electrodes for applications such as energy storage and conversion owing to their unique characteristics, which include substantial surface area, excellent conductivity, abundant surface-terminating groups, and high hydrophilicity. However, MXene nanosheets exhibit a pronounced tendency to restack via Van der Waals force, hindering the active sites and resulting in sluggish electronic and ionic kinetics. This phenomenon limits the capabilities, processability, and overall performance of MXene. In this study, CeO2 is utilized as an interlayer spacer for the Ti3C2 MXene substrate, providing a promising noble metal-free multifunctional electrode. The Ti3C2/CeO2 composite, synthesized via the hydrothermal method, efficiently mitigates restacking while exhibiting excellent conductivity, substantial surface area, and enhanced kinetics. The as-synthesized catalysts undergo diverse physiochemical characterizations and electrochemical measurements to understand their properties and potential multiapplications. The fabricated electrode material, Ti3C2/CeO2, shows excellent specific capacitance of 1908.5 Fg−1 at 1 Ag−1 in a three-electrode setup using 3 M KOH as electrolyte. It has a capacitive retention of 91% even after 4000 cycles. Besides, Ti3C2/CeO2 also functions as a proficient electrode material for overall water splitting, having a lower overpotential of 178 mV and 350 mV for hydrogen and oxygen evolution reactions, respectively, at a current density of 10 mAcm−2. It also displays a lower cell voltage of 1.78 V to obtain a current density of 10 mAcm−2. This study introduces the multi applications of a well-designed interface between Ti3C2 layers and CeO2 within the realm of electrochemical energy storage and conversion.

Copper nanoparticles encapsulated in zeolite 13X for highly selective hydrogenation of CO2 to methanol

High dispersion of active metal is always approved for better catalytic performance in CO2 hydrogenation to methanol. Herein, a strategy was proposed to encapsulate copper nanoparticles in supercages of zeolite 13X, and hence the growth of copper nanoparticles can be controlled. In the present work, catalysts were prepared using ion-exchange and hydrogen reduction at a tiny positive pressure. The results show that as-synthesized catalyst consists of metallic copper and FAU-type zeolite. Excessive amount of copper will destroy zeolite frameworks, and the amount of 5.9 at% is appropriate for considerable BET surface area and ideal copper dispersion. Meanwhile, copper nanoparticles may grow outside from zeolite at high reduction temperatures (≥220 °C), resulting in serious surface area decline and metallic copper agglomeration. Afterwards catalytic tests reveal good stability of the optimal CX-220 catalyst in continuous reactions. The CX-220 achieves remarkably high methanol selectivity of ≥ 95% within wide ranges of reaction temperatures and reaction pressures. Further analyses reveal that the encapsulation of copper nanoparticles reduces micropores and enriches mesopores in zeolite. The apparent activation energy for methanol synthesis over CX-220 catalyst has been lowered to a very low level because of the unique microstructure, and thus the methanol synthesis reaction is dominant in CO2 hydrogenation for dramatic methanol selectivity. Therefore, this work gives important insights and applicable routes for catalysts analyses of CO2 hydrogenation to methanol.

Enhancing the electronic structure of Ni-based electrocatalysts through N element substitution for the hydrogen evolution reaction.

The weak orbital coupling between Ni3N and H2O, caused by its interstitial structure and attenuated Ni-N interaction, is attributed to the high unoccupied d orbital energy of Ni3N. Consequently, the kinetics for water dissociation in the HER are slow. In this study, we effectively lowered the energy state of vacant d orbitals in Ni3N, which resulted in an exceptionally efficient HER. The as-synthesized Ni3N catalyst demonstrates an overpotential of 135 mV when subjected to a current density of 10 mA cm-2. The refined structural characterization suggests that the introduction of oxygen results in a reduction in electron densities surrounding the Ni sites. Furthermore, DFT calculations provide additional evidence that the electrocatalyst of Ni3N generates a greater number of lowest unoccupied orbitals (LUMOs) and improved alignment, thereby enhancing the adsorption and splitting of water. The notion of orbital-regulated electronic levels on Ni sites introduces a distinctive methodology for the systematic development of catalysts used in hydrogen evolution and other applications.

Elucidating the performance of hexamethylene tetra-amine interlinked bimetallic NiCo-MOF for efficient electrochemical hydrogen and oxygen evolution.

Bimetallic metal-organic frameworks (MOFs) play a significant role in the electrocatalysis of water due to their large surface area and availability of increased numbers of pores. For the inaugural time, we examine the effectiveness of a hexamethylene tetra-amine (HMT)-induced 3D NiCo-MOF-based nanostructure as a potent bifunctional electrocatalyst with superior performance for overall water splitting in alkaline environments. The structural, morphological, and electrochemical properties of the as-synthesized bifunctional catalyst were examined thoroughly before analyzing its behavior towards electrochemical water splitting. The HMT-based NiCo-MOF demonstrated small overpotential values of 274 mV and 330 mV in reaching a maximum current density of 30 mA cm-2 for hydrogen and oxygen evolution mechanisms, respectively. The Tafel parameter also showed favorable HER/OER reaction kinetics, with slopes of 78 mV dec-1 and 86 mV dec-1 determined during the electrochemical evaluation. Remarkably, the NiCo-HMT electrode exhibited a double-layer capacitance of 4 mF cm-2 for hydrogen evolution and 23 mF cm-2 for oxygen evolution, while maintaining remarkable stability even after continuous operation for 20 hours. This research offers a valuable blueprint for implementing a cost-effective and durable MOF-based bifunctional catalytic system that has proven to be effective for complete water splitting. Decomposition of water under higher current densities is crucial for effective long-term generation and commercial consumption of hydrogen.

Fe3O4@WO3-E-SMTU-NiII: as an environmentally-friendly, recoverable, durable and noble-free nanostructured catalyst for C-C bond formation reaction in green media.

In the present study, NiII immobilized on Fe3O4@WO3 functionalized by aminated epichlorohydrin using S-methylisothiourea (Fe3O4@WO3-E-SMTU-NiII) as a novel magnetically separable nanostructured catalyst was successfully synthesized and characterized using FT-IR, XRD, TEM, FE-SEM, EDX, EDX mapping, VSM, TGA, H2-TPR, ICP-OES and CHNS techniques. Characterization results revealed the spherical morphology and superparamagnetic behaviour of the as-synthesized catalyst with mean diameters of 19-31 nm as well as uniform distributions of the desired elements (Fe, O, W, C, N, S and Ni). The antibacterial activity of Fe3O4@WO3-E-SMTU-NiII was evaluated against a set of Gram positive and Gram negative bacteria, and the catalyst showed considerable activity against the Staphylococcus aureus strain. The aforementioned nanostructured catalyst exhibited perfect catalytic efficiency in the Heck-Mizoroki and Suzuki-Miyaura reactions under mild conditions without using toxic solvents (EtOH as a green solvent and WEB as a benign base). Desired coupled products were obtained from the reaction of different Ar-X (X = I, Br, Cl) with alkyl acrylates and arylboronic acids. A high nickel content with negligible metal leaching during the course of reactions led to the high catalytic performance and stability of Fe3O4@WO3-E-SMTU-NiII under optimized reaction conditions. The magnetically separation and ease of recovery and reusability of up to six cycles without a discernible decrease in catalytic activity or metal leaching are the most important features of the catalytic system from both industrial and environmental viewpoints.

Heterostructured FeSe2-CoSe2 Nanorods Supported on Nitrogen and Sulfur co-doped Reduced Graphene Oxide as High‐Performance Electrocatalyst for Oxygen Evolution Reaction

With the aim of hydrogen production from electrochemical water splitting on a high scale, the core challenge is to develop an effective oxygen evolution reaction (OER) electrocatalyst with high activity as well as a low cost. Herein, we developed a heterostructure of Iron and cobalt selenide supported by a dual heteroatom (Nitrogen and Sulphur) doped reduced graphene oxide, synthesized by an easy solvothermal method. The as-synthesized CoSe2-based catalyst consists of urchin-like assembled nanorods resulting in the highly exposed reaction sites and shows excellent electrochemical performance with the much lowest overpotentials of 216 mV and 291 mV at a current density of 10 and 50 mA cm−2, respectively, Tafel slope of 53.4 mV dec−1 and long-term stability for 50 h in an alkaline environment. As a result, the improved OER activity of the as-synthesized electrocatalyst could be attributed to the highly accessible heterointerfaces served as abundant catalytic active sites as well as strong synergistic interaction and enhanced electrical conductivity that increased the movement of electron transfer. The achieved results manifest the superiority of the prepared electrocatalyst towards OER and it can be a remarkable electrocatalyst which is helpful for further development in the practical application of water splitting to decrease energy utilization at a high scale.

The promotional effect of Ag in activated carbon supported Pt-Ag nanoalloy electrocatalyst towards alkaline ethanol oxidation reaction: A kinetic study

Due to the scarcity of fossil fuels and their severe environmental consequences, the development of high-efficiency energy conversion devices such as fuel cells (FCs) has gained considerable attention. The specific energy conversion efficiency of FC is highly influenced by the activity of the electrocatalysts. Platinum (Pt) is widely used as an electrocatalyst due to its high activity and stability, but high cost and depletion of resources hinder its commercialization. One of the workable strategies for the practical application of Pt is to reduce its content by alloying with non-precious metals and simultaneously maintain its electrochemical performance. In this context, we developed a low Pt-loaded Pt-Ag/AC alloy electrocatalyst. The electrocatalytic activity and kinetics of the as-synthesized catalyst were evaluated by cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) using the three-electrode electrochemical workstation at room temperature. The electrocatalytic investigations reveal that the resultant AC-supported Pt-Ag with Pt: Ag = 1.8:2.3 at% has higher activity i.e., 32.7 mA cm−2 as compared to that of Pt/AC (20.8 mA cm−2) in an alkaline electrolyte and makes it an efficient electrocatalyst for the electro-oxidation of ethanol. The electron donation from Ag to Pt during the alloying process helps in weakening the interaction with CO and other intermediate species, thereby lowering their binding and poisoning effect on the surface, which may partly be responsible for the improved catalytic performance of Pt-Ag/AC. The activated carbon (AC) support also favors charge transport by reducing ohmic resistance. The cyclic stability studies also reveal that Pt-Ag/AC performs significantly better than Pt/AC with a current retention of 65.2 % and 48.3 % till 1000 cycles, respectively. Therefore, alloying Pt with earth-abundant Ag under rational composition provides optimized surface and electronic properties that result in improved ethanol electro-oxidation activity while reducing the utilization of precious noble metals.

S-doped g-C3N4 for fluorescence sensing of Fe3 + and photocatalytic dye degradation under solar light

Sulfur doped graphitic carbon nitride nanosheets were synthesized via polycondensation reaction of urea-thiourea mixture. Structure and morphology were characterized by XRD (X-ray diffraction), SEM (scanning electron microscope), and XPS (X-ray Photoelectron Spectroscopy). DRS (diffuse reflectance spectroscopy), PL (Photoluminescence spectroscopy) and time-resolved fluorescence decay spectra were used to study the optical characteristics. The photocatalytic dye degradation of Rhodamine B (RhB) in the presence of as-synthesized catalysts was investigated with the help of a UV–visible spectrophotometer. The photocatalytic activity of carbon nitride prepared from urea-thiourea mixture is almost three times higher than that of the pure sample. The detection of Fe3+ was also investigated by using the fluorescence sensing method. The as-synthesized samples hold greater selectivity and sensitivity for fluorescence sensing of Fe3+within a range of 0–3 µM. This range is comparable to the performance of other Fe3+ fluorescent probes previously reported.

Low temperature oxidation of diesel soot particles over one-dimensional 2 × 3 tunnel-structured Na2Mn5O10 catalysts

Tunnel-structured manganese oxides have drawn widespread research attention due to their excellent oxidation properties for the soot oxidation reaction. In this study, a series of romanechite Na2Mn5O10 catalysts with a 2 × 3 tunnel structure were synthesized via a facile hydrothermal method. The as-synthesized catalysts were investigated using X-ray diffraction, scanning and transmission electron microscopy, H2 and soot temperature-programmed reduction, O2 temperature-programmed desorption, NO temperature-programmed oxidation, X-ray photoelectron spectroscopy, and other measurements. Among all the catalysts, the Na1MnyOδ-120 catalyst exhibited the best catalytic performance for soot combustion, with T10, T50, and T90 values of 281 ℃, 317 ℃, and 343 ℃, respectively, which were considerably reduced to 271 ℃, 310 ℃, and 335 ℃ in the existence of 10% H2O. The results of multiple characterization methods indicated that the Na2Mn5O10 catalysts exhibit good reducibility, strong oxygen adsorption and activation capacity, and NO to NO2 oxidation ability. Moreover, the active sites (Mn and oxygen vacancies) and reaction mechanism (Langmuir–Hinshelwood) were also revealed by in-situ DRIFT and density functional theory calculations results. This study details a new strategy for the design and synthesis of efficient soot oxidation catalysts with practical application prospects.

Visible Light Induced Photocatalytic Removal of Methylene Blue Using Cu-tunable p-type ZnO Nanoparticles.

Removal of phototoxicity and zootoxicity pollutants from the aqueous environment is of great importance to human and aquatic life. Copper-tunable p-type zinc oxide (Cu-ZnO) photocatalysts have been prepared by the chemical co-precipitation method. The structural, morphological, elemental and optical properties of the obtained catalysts were characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray (EDX) analysis and ultraviolet-visible (UV-Vis) spectrophotometry. The diffraction patterns of the as-synthesized catalysts were matched with that of the hexagonal wurtzite structure for the standard ZnO nanoparticles. The photocatalytic activity of the prepared Cu-doped ZnO catalyst was evaluated using methylene blue (MB) dye under various conditions. The effect of operational parameters such as MB initial concentration, catalyst dosage, and solution pH was optimized using a face central composite design (FCCD) of the response surface methodology (RSM). The optimum photodegradation efficiency of 98.00% was found at 0.30g/L catalyst dose, 10.00mg/L initial concentration of MB and initial pH at 6.00. The degradation model was statistically remarkable with p < 0.0001% in which the MB initial concentration and solution pH were the most significant variables influencing the removal of MB over the Cu tunable p-type ZnO photocatalyst under visible light irradiation. Finally, the photocatalytic degradation of MB using the undoped and Cu-doped ZnO nanoparticles was nicely fitted pseudo-first-order kinetics scheme.

Ziegler-Natta catalyst particle size control in propylene/α-olefin (co)polymerizations

This study investigates the influence of particle size of Ziegler-Natta (ZN) catalysts on the micro-structure and properties of related polypropylenes. In this regard, three catalysts were synthesized with different particle sizes (PS) including PS < 25, 25 ≤ PS ≤ 45, and PS > 45 μm, but from the same ingredients. The catalyst characterization involved a wide range of methods including TGA, BET, SEM, EDS, XRD, LPS, and N2 adsorption-desorption techniques. Next, a series of propylene homopolymers and their copolymers with 1-hexene were prepared using the as-synthesized catalysts, in the presence or absence of H2 under similar reaction conditions. The synthesized (co)polymers were characterized with DSC, SSA, 13CNMR and TREF techniques. The activity was found to increase with decreasing catalyst particle size in both homo- and copolymerization experiments. Furthermore, a catalyst with a larger particle size provided a polymer with a lower isotacticity index, slightly longer meso sequence length, and higher 1-hexene content of about 10.57 %. This affirms the importance of catalyst/support particle size control during the preparation process in industrial polypropylene plants.

Nickel impregnated graphene oxide catalyst for the desulfurization of transportation fuels using NaClO/H2O2 oxidants

Herein, graphene oxide (GO) and nickel (Ni) impregnated GO (Ni/GO) catalysts were synthesized in combination with NaClO/H2O2 mixture for the oxidative desulfurization (ODS) of model and transportation oils. The as-synthesized catalysts were analyzed via FT-IR, XRD, SEM, BET, and EDX techniques, which revealed that Ni was successfully impregnated over GO surface, which not only increased the surface area and pore volume of the parent GO but also increased the surface functionalities that can adsorb more DBT species. Catalytic results showed that Ni/GO-NaClO/H2O2 system can convert 96% DBT to oxides (1,000 ppm) (sulfur content removed from 173.5 to 17.35) in 90 min at 45 °C using 0.03 g catalyst and 2 mL NaClO/H2O2 (2:2) mixture. Whereas the DBT conversion in gasoline, diesel, and kerosene reached 87%, 66%, and 61%, respectively, at the same optimized conditions and the system was reproducible for five consecutive times with promising ODS activity. The current study credited to its environmental benignity, ease of preparation, and cost-effectiveness could be of great prospect for the industrial-scale processing of transportation oils.

Green catalysis for the production of n-butyl acetate over phosphotungstic acid-encapsulated metal-organic framework UiO-67 catalyst: Catalyst preparation, characterization and reaction kinetics

In the present study, a composite of Keggin-type phosphotungstic acid encapsulated in sized-matched metal-organic framework UiO-67 (HPW@UiO-67) was successfully fabricated via a facile hydrothermal synthesis method and utilized for the preparation of n-butyl acetate. The as-synthesized composite catalyst was comprehensively characterized using FT-IR, PXRD, ICP-OES, N2 adsorption-desorption, SEM, TEM, NH3-TPD, TGA-DTG and XPS techniques. The characterization results confirmed that HPW was successfully immobilized in metal-organic framework without changing the structure of UiO-67. The asprepared HPW@UiO-67 catalyst exhibited higher esterification activity compared to the UiO-67 catalyst due to its suitable surface area and total volume, high dispersion of phosphotungstic acid and high total acidity. The kinetic study indicated that the process followed the second-order kinetic with the activation energy Ea = 53.1 kJ/mol. The catalyst exhibited good recovery and catalytic performance in the reuse study, maintaining the conversion of acetic acid above 63.1% after four reaction cycles. Moreover, the reaction mechanism for the synthesis of n-butyl acetate via esterification over HPW@UiO-67 was proposed.

Visualizing the Birth and Monitoring the Life of a Bimetallic Methanation Catalyst.

Well-defined bimetallic heterogeneous catalysts are not only difficult to synthesize in a controlled manner, but their elemental distributions are also notoriously challenging to define. Knowledge of these distributions is required for both the as-synthesized catalyst and its activated form under reaction conditions, where various types of reconstruction can occur. Success in this endeavor requires observation of the active catalyst via in situ analytical methods. As a step toward this goal, we present a composite material composed of bimetallic nickel-ruthenium nanoparticles supported on a protonated zeolite (Ni-Ru/HZSM-5) and probe its evolution and function as a photoactive carbon dioxide methanation catalyst using in situ X-ray absorption spectroscopy (XAS). The working Ni-Ru/HZSM-5, as a selective and durable photothermal CO2 methanation catalyst, comprises a corona of Ru nanoparticles decorating a Ni nanoparticle core. The specific Ni-Ru interactions in the bimetallic particles were confirmed by in situ XAS, which reveals significant electron transfer from Ni to Ru. The light-harvesting Ni nanoparticle core and electron-accepting Ru nanoparticle corona serve as the CO2 and H2 dissociation centers, respectively. These Ni and Ru nanoparticles also promote synergistic photothermal and hydrogen atom transfer effects. Collectively, these effects enable an associative CO2 methanation reaction pathway while hindering coking and fostering high selectivity toward methane.

Directional Electrosynthesis of Adipic Acid and Cyclohexanone by Controlling the Active Sites on NiOOH.

Dicarboxylic acids and cyclic ketones, such as adipic acid (AA) and cyclohexanone (CHN), are essential compounds for the chemical industry. Although their production by electrosynthesis using electricity is considered one of the most promising strategies, the application of such processes has been hampered by a lack of efficient catalysts as well as a lack of understanding of the mechanism. Herein, a series of monolithic msig/ea-NiOOH-Ni(OH)2/NF were prepared by means of self-dissolution of metal matrix components, interface growth, and electrochemical activation (denoted as msig/ea). The as-synthesized catalysts have three-dimensional cuboid-like structures formed by interconnecting nanosheets composed of NiOOH. By theoretically guided regulation of the amounts of Ni3+ and oxygen vacancies (OV), a 96.5% yield of CHN from cyclohexanol (CHA) dehydrogenation and a 93.6% yield of AA from CHN oxidation were achieved. A combined experimental and theoretical study demonstrates that CHA dehydrogenation and CHN oxidation were promoted by the formation of Ni3+ and the peroxide species (*OOH) on OV. This work provides a promising approach for directional electrosynthesis of high-purity chemicals with in-depth mechanistic insights.