ChemCatChem最新文献

Ruthenium (Ru)- and iridium (Ir)-based nanomaterials have always been regarded as efficient electrocatalysts for oxygen evolution reaction (OER) in acidic electrolytes. Herein, we develop a facile dodecylamine-assisted hydrothermal synthesis for producing carbon-supported IrRu alloy nanoparticles with controllable Ir/Ru ratios and ultrafine sizes towards high-efficiency OER and overall water electrolysis. In this strategy, the dodecylamine that serves as a capping and reducing agent enables the final IrRu alloy nanoparticles to possess average sizes <3 nm and high degree of dispersion on carbon substrate. By combining high OER activity of Ru with high acidic robustness of Ir, the as-prepared IrRu/C nanoparticles at a suitable Ir/Ru ratio of 1/3 show good activity and durability for the OER electrocatalysis and overall water splitting. In specific, the Ir₁Ru₃/C catalyst exhibits the lowest overpotential of 302 mV at the current density of 10 mA cm⁻² and the highest mass activity of 120.5 mA mg⁻¹ at 1.532 V for OER in 0.5 M H₂SO₄ electrolyte. In addition, a two-electrode acidic electrolyzer assembled with Ir₁Ru₃/C at anode and commercial Pt/C at cathode (Pt/C|| Ir₁Ru₃/C) exhibits a low cell voltage of 1.44 V for achieving the current density of 10 mA cm⁻², along with a satisfied 20h durability.

2,5-Furandicarboxylic acid (FDCA) is a biomass-derived monomer for the production of poly(ethylene 2,5-furandicarboxylate) (PEF), which is a novel polyester that can serve as a sustainable alternative to traditional petroleum-based poly(ethylene terephthalate) (PET). Currently, the industrial production of FDCA depends on the thermo catalytic aerobic oxidation of 5-hydroxymethylfurfural (HMF) using heterogeneous catalysts in aqueous solution, in which process equivalent homogeneous bases are usually needed to promote the oxidation of hydroxymethyl and aldehyde groups and simultaneously improve the solubility of oxidative products via forming carboxylate. The involvement of massive base causes risks of equipment corrosion and necessitates subsequent product separation and purification with a large amount acid. In this context, the base-free aerobic oxidation of HMF to FDCA has attracted much concern. Nowadays, by developing supported catalysts with multiple catalytic sites, using diluted substrate and finding good solvent for FDCA, much progress has been achieved in this field. This review provides the state of the art of the heterogeneous catalysis for aerobic oxidation of HMF to FDCA under base-free conditions, highlighting the catalytic mechanism to shed light on the catalyst design principles.

Significant efforts are underway to enhance the efficiency of water electrolysis for sustainable hydrogen production. Approaches that were explored are the design of an efficient anode, engineering of electrolytes, and application of diffusion protective layer over the catalyst to protect it from corrosive reactions. Here we are exploring the engineering of electrode fabrication to enhance the efficacy of anode catalysts by ensuring that the materials are carefully selected. β-MnO₂ has been used to develop a cost-effective method for electrode fabrication that establish a Schottky junction at heterostructure interface. This method transforms commercial RuO₂, which is considered to be less active and stable, highly selective for chlorine oxidative reactions, into a highly active, stable, and OER-selective in alkaline medium and surrogate seawater. With the help of thorough electrochemical techniques, we found that this engineering significantly improves the effective electrochemical surface area, and higher kinetics and conversion per unit site, profoundly affecting the charge transfer mechanism and optimizing the adsorption of OER intermediates, resulting in much-increased mass activity. It is observed that the selectivity of the OER was enhanced due to the Lewis acid repercussions of β-MnO₂.

The modern world's major challenges, such as global warming, air pollution, and increasing energy demands, escalate the importance of sustainable development and transition toward renewables using innovative and environmentally friendly solutions, such as intensifying chemical processes, to reduce carbon footprints effectively. Aiming to enhance the process toward negative carbon emissions, this perspective explores the intensified membrane reactors for reducing the energy intensity of converting biogas into methanol, a versatile chemical feedstock, and renewable liquid fuel. Syngas and methanol synthesis processes, catalysts, and membranes were explored, and novel reactor designs were proposed. Introduction of selective membranes into the catalytic reaction zone to combine synthesis separation steps could enhance the system efficiency and intensify the process by recycling energy and materials, besides reducing costs and required energy for the separation process: the continuous harnessing of products shifts reactions toward desired species while recycling energy and materials enhances the process efficiency, and separating water from methanol reduces the required energy and costs of extra processes for methanol separation. The successful implementation of this technology holds significant promise for sustainable developments in producing chemicals and renewable fuel from renewable biogas and reducing methane and carbon dioxide emissions toward achieving carbon-negative technologies.

The development and exploration of efficient bifunctional electrocatalysts for water splitting are in high demand and have garnered significant attention in recent years. Herein, by incorporating the advantages of catalytically active polyoxometalates (POMs) and structural stable metal–organic frameworks (MOFs), two POM@MOFs composite materials, Ni₄Mo₁₂@Fe and Co₄Mo₁₂@Fe, have been successfully prepared via the encapsulation of POMs anions, [Mo^V₁₂O₃₀(μ₂-OH)₁₀H₂{Ni^II₄(H₂O)₁₂}]∙14H₂O (noted as Ni₄Mo₁₂) and [Mo^V₁₂O₃₀(μ₂-OH)₁₀ H₂{Co^II(H₂O)₃}₄]∙12H₂O (noted as Co₄Mo₁₂), into the cavities of MOFs NH₂-MIL-101(Fe), respectively. Compared to each individual components, Ni₄Mo₁₂@Fe and Co₄Mo₁₂@Fe composites, as heterogeneous electrocatalysts, both showed enhanced electrocatalytic capacities for efficient oxygen evolution reaction (OER) under alkaline conditions with overpotentials of 332.64 mV for Ni₄Mo₁₂@Fe and 352.64 mV for Co₄Mo₁₂@Fe at 10 mA cm⁻². Additionally, the enhanced electrocatalytic capacities of these two composites could also achieve towards hydrogen evolution reaction (HER). Such a POMs-assisted strategy for the formation of POM@MOFs composites, described here, paves a new avenue for the development of highly economical, active nonnoble metal bifunctional electrocatalysts for OER and HER.

Dry reforming of methane (DRM) is a promising catalytic process for converting greenhouse gases (CH₄ and CO₂) into syngas (CO and H₂). This study investigates DRM under moderate conditions (550 °C) using supported low-loading (0.05 wt%) metal (M) catalysts (M = Rh, Ru, Pt, Pd, Ir, Au, and Ni). The reaction was carried out for 6 h with a flow rate of 30 mL/min for both CH₄ and CO₂, using 0.10 g of catalyst. Among these catalysts, 0.05 wt% Rh/Al₂O₃ exhibited the highest DRM activity. The effect of catalyst supports revealed that Al₂O₃ is the most effective support for 0.05 wt% Rh. The DRM activity of Rh species supported on Al₂O₃ and SiO₂ was compared, and the Rh species on Al₂O₃ outperformed those on SiO₂, indicating Al₂O₃ enhances the DRM activity of Rh. When comparing the DRM activity of Rh nanoparticles and Rh single atoms, it was suggested that Rh nanoparticles might exhibit superior performance for DRM. Coke deposited on 0.05 wt% Rh/Al₂O₃ is removed by CO₂, maintaining stable catalytic activity. These findings provide valuable insights into the design of catalysts that minimize the use of noble metals in DRM reactions.

The shape-defined ZnFe₂O₄ spinel with cubic and octahedral morphology was hydrothermally synthesized, respectively, and used as catalyst precursor for Fischer–Tropsch synthesis (FTS). The structure of ZnFe₂O₄ spinel was changed to ZnO and Fe₅C₂ (Fe₅C₂/ZnO) after reduction and carbonization. Interestingly, ZnFe₂O₄ with cubic morphology exhibited much higher catalytic activity and selectivity toward low-carbon olefins (C₂–C₄) than the octahedral one under identical conditions, and the latter tended to produce the saturated alkanes. The primary properties of ZnFe₂O₄ materials before and after reduction were systematically studied through a series of characteristic technologies to reveal the difference in catalytic performance between the two ZnFe₂O₄ spinels with different morphologies.

The use of catalase (CAT) from bovine liver as an electrocatalyst in the air electrode of a primary zinc–air battery (ZAB) with neutral electrolyte (pH 7.4) is reported. First, the use of Nafion for immobilizing CAT onto electrode surface allowed to obtain long-term stability of the catalytic activity of CAT. Besides, analysis of the CAT and CAT-Nafion as catalysts for oxygen reduction reaction (ORR) was carried out by linear sweep voltammetry (LSV) using a rotating ring-disk electrode (RRDE), demonstrating a four-electron ORR mechanism. Finally, CAT and CAT-Nafion were tested as air electrodes in flooded ZAB and compared against human hemoglobin-based ZAB. Our results demonstrated the significant influence of the protein coating of the heme groups on the ZAB performance, affecting greatly the discharge capacity and the power density.

Herein, we have reported a sustainable and chemo-selective strategy for the synthesis of functionalized branched alcohols. A commercially available catalytic system does not need any special ligand and liberated water and hydrogen as side products. A series of alkyl primary alcohols (C4–C10), including methanol, were tolerated in good to high yield. Sequential transformations to substituted pyrroles, chromenes and synthesis of donepezil drug were obtained (>57 entries). Preliminary mechanistic investigations were performed to understand the catalytic pathways.

Thiolate-protected Au nanoclusters (NCs) have developed as a promising class of model catalysts to achieve fundamental understanding of metal nanocatalysis. Whereas, the packing mode of peripheral ligand on metal core is changeful in the reaction medium and show elusive impact on catalytic activity. In this work, using glutathione (GSH) protected Au NCs (Au@GSH NCs) with aggregation-induced-emission (AIE) characteristics as model catalyst for the hydrogenation of 4-nitrophenol (4-NP), photoluminescence (PL) intensity correlated catalytic activity of Au@GSH NCs was successfully mediated by the addition of Ag⁺ in the preparation or poor solvent in the reaction medium, showing a relationship of “as one falls, another rises.” Au NCs with intense PL implied a dense packing of peripheral ligand, which hampered the accessibility of active site and thus exhibited slowest catalytic reaction kinetics of the reduction of 4-NP and vice versa. Based on this methodology, a case study of the effect of salt additives on the catalytic activity is carried out, different mechanisms are distinguished by the change in the PL intensity, and with the combination of diagnostic deuterium isotope experiments, it has been demonstrated that the proton from water solvent is involved in the reaction and that the proton transfer process is the rate-determining step, the contribution of ionic additives to the hydrogen bonding network determines their effect on the reaction kinetics. The correlation between PL intensity and catalytic activity of Au NCs could provide an efficient way to design highly active Au NC catalysts and give a new insight to understand the unique optoelectronic properties of Au NCs and reaction mechanism.