Catalytic Potential Research Articles

Oxidation of Ammonia Catalyzed by a Molecular Iron Complex: Translating Chemical Catalysis to Mediated Electrocatalysis.

Ammonia is a promising candidate in the quest for sustainable, clean energy. With its capacity to serve as an energy carrier, the oxidation of ammonia opens avenues for carbon-neutral approaches to address worldwide growing energy needs. We report the catalytic chemical oxidation of ammonia by an Earth-abundant transition metal complex, trans-[LFeII(MeCN)2][PF6]2, where L is a macrocyclic ligand bearing four N-heterocyclic carbene (NHC) donors. Using triarylaminium radical cations in MeCN, up to 182 turnovers of N2 per Fe were obtained from chemical catalysis with an extremely low loading of the Fe catalyst (0.043 mM, 0.004 mol % catalyst). This chemical catalysis was successfully transitioned to mediated electrocatalysis for the oxidation of ammonia. Molecular electrocatalysis by the Fe catalyst and the mediator (p-MeOC6H4)3N exhibited a catalytic half-wave potential (Ecat/2) of 0.18 V vs [Cp2Fe]+/0 in MeCN, and achieved 9.3 turnovers of N2 at an applied potential of 0.20 V vs [Cp2Fe]+/0 at -20 °C in controlled-potential electrolysis, with a Faradaic efficiency of 75 %. Based on computational results, the catalyst undergoes sequential oxidation and deprotonation steps to form [LFeIV(NH2)2]2+, and thereafter bimetallic coupling to form an N-N bond.

Synthesis, Structural Analysis, and Peroxidase-Mimicking Activity of AuPt Branched Nanoparticles.

Bimetallic nanomaterials have generated significant interest across diverse scientific disciplines, due to their unique and tunable properties arising from the synergistic combination of two distinct metallic elements. This study presents a novel approach for synthesizing branched gold-platinum nanoparticles by utilizing poly(allylamine hydrochloride) (PAH)-stabilized branched gold nanoparticles, with a localized surface plasmon resonance (LSPR) response of around 1000 nm, as a template for platinum deposition. This approach allows precise control over nanoparticle size, the LSPR band, and the branching degree at an ambient temperature, without the need for high temperatures or organic solvents. The resulting AuPt branched nanoparticles not only demonstrate optical activity but also enhanced catalytic properties. To evaluate their catalytic potential, we compared the enzymatic capabilities of gold and gold-platinum nanoparticles by examining their peroxidase-like activity in the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). Our findings revealed that the incorporation of platinum onto the gold surface substantially enhanced the catalytic efficiency, highlighting the potential of these bimetallic nanoparticles in catalytic applications.

CTAB-assisted synthesis of reduced graphene oxide supported Pd nanoparticles (Pd@rGO) as a sustainable heterogeneous catalyst for C-2 arylation of indoles with arylboronic acids

A series of Pd nanoparticles (NPs) incorporated in reduced graphene oxide (rGO), viz. Pd@rGO0.16, Pd@rGO0.32, Pd@rGO0.48, and Pd@rGO1 were synthesized employing water as a solvent. The subscript values correspond to the millimoles of cetyltrimethylammonium bromide (CTAB) utilized in the synthesis process. The quantity of CTAB was varied to finely tune both the morphology and size of the resulting nanoclusters. Transmission Electron Microscopy (TEM) analysis indicated that the average particle sizes of Pd@rGO0.16 and Pd@rGO0.32 fall in the range of 4.5–5.0 nm and 20–25 nm, respectively. On the other hand, particles were found to be agglomerated in Pd@rGO0.48 and Pd@rGO1. The Pd@rGO0.16 composite was exhaustively characterized by TEM, Scanning Electron Microcopy-Energy Dispersive X-ray analysis (SEM-EDX), powder X-ray diffraction(XRD), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma atomic emission spectroscopy (ICP-AES) measurements. ICP-AES analysis of Pd@rGO0.16 indicated that 0.01 g of Pd@rGO0.16 contains 0.09 mol% Pd. The catalytic potentiality of these NPs was investigated for direct C(sp[1])-H bond activation of various indoles with aryl boronic acids. Among the four composites, Pd@rGO0.16 exhibited the best activity for the abovementioned organic transformation. Different indoles with diverse electronic groups underwent coupling with aryl boronic acids giving up to 86 % product yield. It was retrievable for up to five consecutive catalytic cycles without compromising its catalytic activity.

Antimicrobial framework nucleic acid‐based DNAzyme cluster with high catalytic efficiency

AbstractBACKGROUNDHydroxyl radical‐mediated materials primarily liberate more reactive and acutely lethal hydroxyl radical (•OH) and act as potent bactericidal antibiotics, for example H2O2. Hydroxyl radical possess higher tendency than that of H2O2 to attack various biological molecules such as DNA, proteins and iron–sulfur clusters, and impair their proper functioning, actively leading to strongly potent bactericidal effect. To acquire the desired antimicrobial effect, high concentration of H2O2 is required that has found medically harmful to healthy tissues of humans.RESULTSWe herein report framework nucleic acid‐regulated DNAzyme cluster (FDC) – that is, peroxidase‐like hemin‐bound G‐quadruplex (G4/H) DNAzyme – to amplify the catalytic reduction potential of G4/H complex, leading to high conversion rate of H2O2 to more reactive hydroxyl radical that potentially shows the same antibacterial efficiency at lower and safer H2O2 concentration. Specifically, we have grafted multiple copies of DNAzymes outside framework nucleic acid (FNA) to successively achieve 3–9 orders of magnitude enhancement in catalytic activity and antibacterial efficiency of FDC.CONCLUSIONOur designed FDC has successfully alleviated H2O2 toxicity and increased its efficiency as antibacterial material, as FDC amplified the catalytic reduction potential of G4/H DNAzyme, leading to high conversion rate of H2O2 to more reactive •OH that potentially shows the same antibacterial efficiency at lower and safer H2O2 concentration. © 2024 Society of Chemical Industry (SCI).

The g-C3N4/CdO heterojunction as an efficient photo-electron catalyst for hydrogen production

The electronic, optical, and photo-electro catalytic properties of the g-C3N4/CdO(CGN/CdO) heterojunction are studied by Density Functional Theory (DFT) calculations. The CGN/CdO heterojunction has a staggered band structure and indirect bandgap (1.976 eV), following the S-scheme mechanism. The absorption spectra of the heterojunction are substantially red-shifted and the absorption coefficients are significantly higher relative to the intrinsic g-C3N4(GCN) and intrinsic CdO. In addition, the power conversion efficiency (PCE) is 14.21 %. The photo-catalytic water decomposition can occur at pH = 0–14. The ηSTH of the GCN/CdO heterojunction is up to 31.82 %, and it is modulated to 36.14 % under −4 % biaxial strain modulation. The low over-potential of the Oxygen evolution reaction (OER) for the heterojunction is 0.905 V obtained at the GCN layer, and that of the Hydrogen evolution reaction (HER) is −0.498 V occurred at the CdO layer. These findings suggest that the GCN/CdO heterojunction has an efficient photo-electro catalytic potential for hydrogen production.

Mesoporous MPC@TMG, a basic heterogeneous organocatalyst in C–C/C–N bond forming reactions: Tandem multicomponent synthesis of 5-amino-pyrazole-4-carbonitriles and 1H-pyrazolo [1,2-b] phthalazine-5, 10-dione derivatives under sustainable reaction conditions

A metal-free, effective, and sustainable protocol has been developed to carry out C–N and C–C bond-forming reactions leading to the formation of 5-amino-pyrazole-4-carbonitriles and 1H-pyrazolo [1,2-b] phthalazine-5, 10-dione derivatives via a tandem multicomponent reaction using mesoporous MPC@TMG as a basic heterogeneous organocatalyst. The reactions were performed in aqueous medium at room temperature. The synthesized organocatalyst MPC@TMG was characterized by numerous spectroscopic techniques such as Fourier Transform Infrared (FTIR), Powder X-ray diffraction (PXRD), Brunauer-Emmett-Teller (BET), Scanning Electron Microscope (SEM), Energy Dispersive X-ray (EDX), elemental mapping, and Thermal Gravimetric (TG) analyses. MPC@TMG displayed excellent catalytic potential, high thermochemical stability, and reusability for up to eight catalytic runs and offered the title compounds in excellent yields (>90 %) in a short reaction time (6–15 min). The synthesized compounds were characterized through FTIR, 1H, and 13C Nuclear Magnetic Resonance (NMR) spectroscopy. The use of water as a green solvent, the generality of the method, easy catalyst recovery, a simple work-up procedure, and zero involvement of any metal are the key features of the present protocol making it green and sustainable for the synthesis of the desired heterocycles and is supported by the calculations for green metrics parameters.

Exploration of the catalytic, anti-bacterial, and anti-oxidant capabilities of environmentally conscious zinc oxide nanoparticles synthesized using Citrus sinensis

Zinc oxide nanoparticles have been fabricated via a sustainable protocol from the fruit juice of Citrus sinensis. The SEM and TEM analyses were employed to ascertain the morphology and particle size of the nanoparticles, unveiling a spherical shape and a particle size ranging from 40 to 60 nm. XRD study suggested that the nanoparticles were crystalline. FT-IR analysis displayed bands for the possible phytochemicals involved in the bio-reduction and capping of the nanoparticles. The nanoparticles' ability to inhibit the growth of four bacterial strains-Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa was evaluated to determine their antimicrobial effectiveness. The nanoparticles showed significant anti-microbial action against the tested strains. DPPH assay was accomplished to evaluate the anti-oxidant activity of the nanoparticles, wherein a reasonable free radical scavenging ability of 65.87 % (IC50 = 366.37 μg/mL) was attained. The nanoparticles displayed substantial catalytic activity for the reduction of the organic dye-malachite green. The dye degradation of 91.87 % was achieved in 21 min and the reaction kinetics was pseudo-first-order. The nano-catalyst was reusable for three sequential cycles of the reduction reaction and no substantial decrease in its catalytic potential was observed. Hence, the eco-friendly approach to synthesizing zinc oxide nanoparticles proved to be successful and the nanoparticles exhibited an array of promising applications.

Exploring Structural Evolution Behaviors of Ligand‐Defect‐Rich Ferrocene‐Based Metal‐Organic Frameworks for Electrochemical Oxygen Evolution via Operando X‐Ray Absorption Spectroscopy

AbstractMetal‐organic frameworks (MOFs) have exhibited encouraging catalytic activity for the oxygen evolution reaction (OER), a crucial process for water electrolysis to produce green hydrogen. Nonetheless, distinguishing the source of catalytic activity and establishing the structure‐composition‐property relationships of MOFs during OER processes remain challenging. Here, for the first time, operando X‐ray absorption spectroscopy (XAS) is utilized to monitor the structural evolution and identify the active components of ferrocene‐based MOFs (Ni‐Fc) for OER. Ligand‐defect‐rich Ni‐Fc is synthesized via the co‐deposition method. After electrochemical activation, Ni‐Fc exhibits superior electrocatalytic activity (228 mV at 10 mA cm−2 in 0.1 m KOH), which is highly competitive compared with state‐of‐the‐art electrocatalysts. Operando XAS analysis and ex‐situ characterizations reveal the structural reconstruction of Ni‐Fc into amorphous NiFe‐catalysts (a‐NiFe) during the activation process, and further into real catalytic phases (a‐NiFe‐C) under catalytic potential greater than 1.45 V (vs RHE). In catalytic phases, in‐situ formed deprotonated and oxygen‐defected Ni oxyhydroxide analogues act as catalytic sites, while Fe hydroxide analogues derived from ligands optimize the electronic structure of Ni sites for improving OER activity. Density functional theory (DFT) analysis indicates a reduced energy barrier in a‐NiFe‐C compared to pristine MOFs, supporting the improved catalytic activity of the latter.

Synthesis of Vanadyl Complexes of N-Confused Porphyrins and Their Bromoperoxidase-like Catalytic Activity.

Two new vanadyl complexes of N-confused porphyrins (NCPs), [VONCTPP] (V-1) and [VONCP(OMe)8] (V-2), have been synthesized for the first time and investigated as a catalyst for the oxidative bromination reaction of phenol and its derivatives. This article further delineates crystal structures, photophysical, and redox properties of both the vanadyl complexes. Complexes V-1 and V-2 exhibited a significant red shift in their absorption spectra compared with their respective free bases. The single-crystal structure of V-1 revealed that the complex is in the 2H tautomeric form, while EPR studies revealed the +4 oxidation state of vanadium metal having an axial compression with dxy1 configuration. Catalytic potential for bromoperoxidases-like activity has been explored for both complexes V-1 and V-2 for the first time in NCP chemistry with excellent TOF values (4.7-6.3 s-1 for V-1 and 7.3-8.7 s-1 for V-2) using KBr as a source of bromine and H2O2 as a green oxidant in aqueous acidic medium at 298 K. Notably, both catalysts show excellent recyclability over five cycles. The vanadyl-metalated NCPs exhibit excellent stability in the air.

Nanoengineering of mono (Au, Ag) and bimetallic (Ag-Au) alloy nanoparticles for dye degradation and toxicity assessment

This research entails the synthesis and catalytic exploration of bimetallic nanoparticles combining silver (Ag) and gold (Au). The Au concentration was systematically varied (20%, 40%, 60%, and 80%), alongside the utilization of CTAB surfactant for nanoparticle stabilization. UV visible spectroscopic analysis confirmed the formation and stability of synthesized Au, Ag and bimetallic (Ag-Au) nanoparticles. FESEM further confirmed the formation of uniform sized Au and Ag nanoparticles. Integration of Au into Ag resulted in bimetallic (Ag-Au) alloy nanoparticles with smaller dimensions as compared to individual Au and Ag nanoparticles. EDX spectra and mapping verified the composition of each synthesized bimetallic nanoparticle variant. The catalytic potential of the synthesized nanoparticles was methodically explored using UV–visible spectroscopy. All the synthesized nanoparticles showcased excellent catalytic efficacy. The synergistic effect of the alloyed bimetallic nanoparticles was found promising. Assessment of dye toxicity pre- and post-degradation was conducted using the ECOSAR program, indicating a reduction in dye toxicity following degradation.

Optimizing orange II wastewater treatment: Unveiling the catalytic potential of nitrate and iodide ions in ultraviolet photolysis

The rapid ultraviolet photolysis of Orange II (OII) was investigated in a simulated wastewater containing nitrate and iodide ions (UV/NO3−-I− system). The study examined the various factors influencing OII degradation. Direct photolysis was found to have a negligible impact, and OII degradation primarily relied on indirect photolysis. In the UV/NO3−-I− system, OII was completely removed, and the kinetic constants for this system were 5.3 and 3.3 times higher than those for the UV/I− and UV/NO3− systems, respectively. Active substance quenching experiments and electron paramagnetic resonance spectroscopy revealed that hydroxyl radicals played a crucial role in OII degradation. The degradation pathway of OII was proposed using density functional theory calculations and liquid chromatography-mass spectrometry. The figure-of-merit electrical energy per order for the UV/NO3−-I− system was significantly lower than the UV/I− and UV/NO3− systems. Toxicity analysis also showed that UV/NO3−-I− system reduced ecotoxicity of OII. Therefore, the UV/NO3−-I− system holds promise for practical applications in the degradation of organic pollutants.

The Catalytic Potential of Modified Clays: A Review

The need for innovative catalysts and catalytic support materials is continually growing due to demanding requirements, stricter environmental demands, and the ongoing development of new chemical processes. Since about 80% of all industrial processes involve catalysts, there is a continuing need to develop new catalyst materials and supports with suitable qualities to meet ongoing industrial demands. Not only must new catalysts have tailored properties, but they must also be suitable for large-scale production through environmentally friendly and cost-effective processes. Clay minerals, with their rich history in medicine and ceramics, are now emerging as potential catalysts. Their transformative potential is exemplified in applications such as hydrogenating the greenhouse gas CO2 into carbohydrate fuel, a crucial step in meeting the rising electrical demand. Moreover, advanced materials derived from clay minerals are proving their mettle in diverse photocatalytic reactions, from organic dye removal to pharmaceutical pollutant elimination and photocatalytic energy conversion through water splitting. Clay minerals in their natural state show a low catalytic activity, so to increase their reactivity, they must be activated. Depending on the requirements of a particular application, selecting an appropriate activation method for modifying a natural clay mineral is a critical consideration. Traditional clay mineral processing methods such as acid or alkaline treatment are used. Still, these have drawbacks such as high costs, long processing times, and the formation of hazardous by-products. Other activation processes, such as ultrasonication and mechanical activation routes, have been proposed to reduce the production of hazardous by-products. The main advantage of ultrasonication and microwave-assisted procedures is that they save time, whereas mechanochemical processing is simple and efficient. This short review focuses on modifying clay minerals using various new methods to create sophisticated and innovative new materials. Recent advances in catalytic reactions are specifically covered, including organic biogeochemical processes, photocatalytic processes, carbon nanotube synthesis, and energy conversion processes such as CO2 hydrogenation and dry reforming of methane.

Efficient Synthesis of All-silica DDR Zeolite

Zeolite DDR is a small pore zeolite with high application potential in catalysis, adsorption and membrane separation. However, its application is greatly limited by lengthy synthesis time. Various approaches, such as fast heating, reactive raw silica source, special mineralizing agent, seeding, and high synthesis temperature were combined to accelerate crystallization kinetics. The obtained DDR samples were systematically characterized by XRD, SEM, NMR and nitrogen adsorption-desorption. The fastest synthesis was realized by combining microwave radiation, and active (NH4)2SiF6 as silica source, in which high quality DDR zeolite with high yield was obtained in only 5 min. Moreover, replacing toxic (NH4)2SiF6 with safe silica sol led to improved process environment-friendliness and longer synthesis time of 10 min. Finally, replacing expensive microwave heating with economical oil-bath heating resulted into efficient synthesis of zeolite DDR in only 15 min, which would facilitate its commercial applications in adsorption, catalysis and membrane separation.

Innovative strategy for the effective utilization of coal waste slag in the Fenton-like process for the degradation of trichloroethylene

In response to environmental concerns at the global level, there is considerable momentum in the exploration of materials derived from waste that are both sustainable and eco-friendly. In this study, CS-Fe (carbon, silica, and iron) composite was synthesized from coal gasification slag (CGS) and innovatively applied as a catalyst to activate PS (persulfate) for the degradation of trichloroethylene (TCE) in water. Scanning electron microscope (SEM), fourier transmission infrared spectroscopy (FTIR), energy dispersive x-ray spectroscopy (EDS), brunauer, emmet, and teller (BET) technique, and x-ray diffractometer (XRD) spectra were employed to investigate the surface morphology and physicochemical composition of the CS-Fe composite. CS-Fe catalyst showed a dual nature by adsorption and degradation of TCE simultaneously, displaying 86.1% TCE removal in 3 h. The synthesized CS-Fe had better adsorption (62.1%) than base material CGS (36.4%) due to a larger BET surface area (770.8 m2 g−1), while 24.0% TCE degradation was recorded upon the activation of PS by CS-Fe. FTIR spectra confirmed the adsorption and degradation of TCE by investigating the used and fresh samples of CS-Fe catalyst. Scavengers and Electron paramagnetic resonance (EPR) analysis confirmed the availability of surface radicals and free radicals facilitated the degradation process. The acidic nature of the solution favored the degradation while the presence of bicarbonate ion (HCO3−) hindered this process. In conclusion, these results for real groundwater, surfactant-added solution, and degradation of other TCE-like pollutants propose that the CS-Fe composite offers an economically viable and favorable catalyst in the remediation of organic contaminants within aqueous solutions. Further investigation into the catalytic potential of coal gasification slag-based carbon materials and their application in Fenton reactions is warranted to effectively address a range of environmental challenges.

P-block germanenes as a promising electrocatalysts for the oxygen reduction reaction.

The oxygen reduction reaction (ORR), a pivotal process in hydrogen fuel cells crucial for enhancing fuel cell performance through suitable catalysts, remains a challenging aspect of development. This study explores the catalytic potential of germanene on Al (111), taking advantage of the successful preparation of stable reconstructed germanene layers on Al (111) and the excellent catalytic performance exhibited by germanium-based nanomaterials. Through first-principles calculations, we demonstrate that the O2molecule can be effectively activated on both freestanding and supported germanene nanosheets, featuring kinetic barriers of 0.40 and 0.04eV, respectively. The presence of the Al substrate not only significantly enhances the stability of the reconstructed germanene but also preserves its exceptional ORR catalytic performance. These theoretical findings offer crucial insights into the substrate-mediated modulation of germanene stability and catalytic efficiency, paving the way for the design of stable and efficient ORR catalysts for future applications.

Catalytic Nanomedicine: Coated bionanocatalysts for Catalytic Antineoplastic activity

Glioma tumors are the most common form of central nervous system tumors, and there is a pressing need for innovative methods that can precisely target cancer cells while leaving healthy tissues unharmed. In this study, progressing in the field of Catalytic Nanomedicine, we investigated the cytotoxic effects of a novel class of bionanocatalysts on glioma cancer cells. These bionanocatalysts were constructed from a catalytic matrix of oxides with evenly dispersed superficial copper-coating nanoparticles. This design optimizes both the inherent catalytic characteristics of the matrix and instills cytotoxic properties. The bionanocatalysts coated with copper demonstrated a significant reduction in cancer cell viability when compared to reference bionanocatalysts without the transition metal. We also observed structural damage to the cytoskeleton and alterations in mitochondrial activity. These findings suggest that these pathways are integral to the mechanisms through which these nanostructures execute their bionanocatalytic activities, particularly in breaking chemical bonds. Importantly, our physicochemical analyses verified that the coating with copper species, primarily CuO, did not disrupt the individual structure of the bionanocatalysts: instead, it enhanced their catalytic cytotoxic potential. This research aims to deepen our understanding of the mechanisms underlying this promising antineoplastic treatment and underscore the effectiveness of superficial copper-coating nanoparticles as agents for amplifying the inherent properties of bionanocatalysts through nanocatalysis.

Advances in Functional Ceramics for Water Splitting: A Comprehensive Review

The global demand for sustainable energy sources has led to extensive research regarding (green) hydrogen production technologies, with water splitting emerging as a promising avenue. In the near future the calculated hydrogen demand is expected to be 2.3 Gt per year. For green hydrogen production, 1.5 ppm of Earth’s freshwater, or 30 ppb of saltwater, is required each year, which is less than that currently consumed by fossil fuel-based energy. Functional ceramics, known for their stability and tunable properties, have garnered attention in the field of water splitting. This review provides an in-depth analysis of recent advancements in functional ceramics for water splitting, addressing key mechanisms, challenges, and prospects. Theoretical aspects, including electronic structure and crystallography, are explored to understand the catalytic behavior of these materials. Hematite photoanodes, vital for solar-driven water splitting, are discussed alongside strategies to enhance their performance, such as heterojunction structures and cocatalyst integration. Compositionally complex perovskite oxides and high-entropy alloys/ceramics are investigated for their potential for use in solar thermochemical water splitting, highlighting innovative approaches and challenges. Further exploration encompasses inorganic materials like metal oxides, molybdates, and rare earth compounds, revealing their catalytic activity and potential for water-splitting applications. Despite progress, challenges persist, indicating the need for continued research in the fields of material design and synthesis to advance sustainable hydrogen production.

Enhancement of Ni-NiO-CeO2 Interaction on Ni-CeO2/Al2O3-MgO Catalyst by Ammonia Vapor Diffusion Impregnation for CO2 Reforming of CH4.

Ni-based catalysts have been widely used for the CO2 reforming of methane (CRM) process, but deactivation is their main problem. This study created an alternative electronic Ni-NiO-CeO2 interaction on the surface of 5 wt% Ni-5 wt% CeO2/Al2O3-MgO (5Ni5Ce(xh)/MA) catalysts to enhance catalytic potential simultaneously with coke resistance for the CRM process. The Ni-NiO-CeO2 network was developed on Al2O3-MgO through layered double hydroxide synthesis via our ammonia vapor diffusion impregnation method. The physical properties of the fresh catalysts were analyzed employing FESEM, N2 physisorption, and XRD. The chemical properties on the catalyst surface were analyzed employing H2-TPR, XPS, H2-TPD, CO2-TPD, and O2-TPD. The CRM performances of reduced catalysts were evaluated at 600 °C under ambient pressure. Carbon deposits on spent catalysts were determined quantitatively and qualitatively by TPO, FESEM, and XRD. Compared to 5 wt% Ni-5 wt% CeO2/Al2O3-MgO prepared by the traditional impregnation method, the electronic interaction of the Ni-NiO-CeO2 network with the Al2O3-MgO support was constructed along the time of ammonia diffusion treatment. The electronic interaction in the Ni-NiO-CeO2 nanostructure of the treated catalyst develops surface hydroxyl sites with an efficient pathway of OH* and O* transfer that improves catalytic activities and coke oxidation.

Investigating H-atom reactions in small PAHs with imperfect aromaticity: A combined experimental and computational study of indene (C9H8) and indane (C9H10).

Polycyclic aromatic hydrocarbons (PAHs) are widely recognized as catalysts for interstellar H2 formation. Extensive exploration into the catalytic potential of various PAHs has encompassed both theoretical investigations and experimental studies. In the present study, we focused on studying the reactivity of an imperfect aromatic molecule, indene (C9H8), and its hydrogenated counterpart, indane (C9H10), as potential catalysts for H2 formation within the interstellar medium. The reactions of these molecules with H atoms at 3.1K were investigated experimentally using the para-H2 matrix isolation technique. Our experimental results demonstrate that both indene and indane are reactive toward H atoms. Indene can participate in H-atom-abstraction and H-atom-addition reactions, whereas indane primarily undergoes H-atom-abstraction reactions. The H-atom-abstraction reaction of indene results in the formation of the 1-indenyl radical (R1) (C9H7) and H2molecule. Simultaneously, an H-atom-addition reaction forms the 1,2-dihydro-indene-3-yl radical (R2) (C9H9). Experiments also reveal that the H-atom-abstraction reaction of indane also produces the R2 radical. To the best of our knowledge, this study represents the first reporting of the infrared spectra of R1 and R2 radicals. The experimental results, combined with theoretical findings, suggest that indane and indene may play a role in the catalytic formation of interstellar H2. Furthermore, these results imply a quasi-equilibrium between the investigated molecules and the formed radicals via H-atom-addition and H-atom-abstraction reactions.

Insight into the correlation between Cu species and methanol selectivity from CO2 hydrogenation over Cu-based catalyst

The pre-activation of Cu-based catalysts is an important step to fully develop their catalytic potential. The production of active species (Cu+ and Cu0) which play the active site role generally occurs in the activation stage by reducing from Cu2+. Herein, the Cu+/Cu0 ratio of CuZnOAl2O3 (CZA) catalysts was adjusted using different activation atmospheres and the relationship between Cu+/Cu0 ratio of the catalyst and methanol selectivity from CO2 hydrogenation was investigated in detail. Combined with X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), in situ diffuse reflectance infrared Fourier transformation spectroscopy (DRIFTS) characterization, etc. and experimental results, it was observed that the selectivity of methanol was obviously relied on the Cu+/Cu0 ratio of CZA catalyst. This work provides theoretical guidance and feasible scheme to rationally design and optimize the required catalysts.