Catalysis Science & Technology最新文献

Ammonia (NH₃) is one of the most important synthetic inorganic commodities. The current industrial NH₃ production is dominated by the Haber–Bosch process with high energy cost and CO₂ emission as well as the need for large-scale centralized operation. Liquid metals and molten salts have recently emerged as promising catalytic materials for NH₃ synthesis. Herein, we present a molten system comprising Li–Zn alloy and eutectic LiCl–KCl salt for effective NH₃ synthesis at 400 °C and 1 bar. The 70 mol% Li–Zn liquid alloy activates N₂ dissociation more easily than the pure liquid Zn and the 60 mol% Li–Sn liquid alloy. Effective N₂ fixation by the liquid Li–Zn alloy is followed by the hydrogenation of Li₃N dissolved in the molten salt above. For the first time, this work reports a volcano-type relationship between the Li₃N concentration in the molten salt and the NH₃ synthesis rate when feeding H₂ to the molten salt. Ab initio molecular dynamics simulations suggest that, within this system, both N₂ cleavage and Li₃N hydrogenation are quite reactive. Through combined experiments and simulations, this work unravels the molecular mechanisms of nitrogen fixation and ammonia synthesis in the liquid alloy–salt catalytic system, and also demonstrates effective strategies for improving the ammonia synthesis rate. Such a hybrid molten catalytic system offers a promising solution for distributed NH₃ production with low energy cost and CO₂ emission.

H₂O₂ is a green oxidant, which is widely used in chemical production, environmental remediation, sustainable energy conversion and the medical industry. The traditional anthraquinone method for producing H₂O₂ is facing issues, such as potential safety hazards and environmental pollution. Therefore, green and sustainable production of H₂O₂ is desirably investigated. Solar-driven photocatalytic synthesis of H₂O₂ is a promising method, which requires no additional energy input and will not produce new pollution. g-C₃N₄ is a kind of nonmetallic photocatalyst, which has the advantages of low cost, environmental friendliness and high stability. However, g-C₃N₄ still faces the problems of a narrow visible light response range, low photo-generated electron/hole separation efficiency and short carrier lifetime. The polymer properties of g-C₃N₄ are conducive to introducing foreign atoms into the main body of the tri-s-triazine structure. The electronic structure and optical properties of g-C₃N₄ can be adjusted by doping, which can significantly improve the photocatalytic performance of g-C₃N₄. In this work, phosphorus doped g-C₃N₄ (P/g-C₃N₄) is prepared by a simple chemical vapor deposition method. The doping process also introduced defects in the bulk phase of g-C₃N₄, which overcomes drawbacks such as weak visible light capturing ability, low charge separation and transfer efficiency, and a slow mass transfer rate. In addition, the optimized conduction band position further enhances the reduction ability of photo-generated electrons, making its photocatalytic performance magnify by one order of magnitude compared to that of pure g-C₃N₄. Driven by visible light, P/g-C₃N₄ produces H₂O₂ through the photocatalytic oxygen reduction reaction (ORR) in 2 h, reaching a high concentration of 1460.22 μM, and it also maintains good catalytic repeatability in three-cycle catalytic experiments. P/g-C₃N₄ achieves the goal of efficient, stable and green synthesis of H₂O₂.

The interest in multi-enzyme cascades for the synthesis of pharmaceutically relevant active ingredients has increased in recent years. Through a smart selection of enzymes, cascades enable multi-step synthesis in a one-pot reaction without the purification of intermediates. In this study, a five-enzyme cascade for the formation of cyclic 2′3′-GMP-AMP (2′3′-cGAMP) from adenosine and guanosine in seven reaction steps was successfully developed. First, the substrate scope of kinases for the phosphorylation of nucleosides and nucleotides was investigated, which were then combined in an enzyme cascade for 2′3′-cGAMP formation from adenosine, guanosine, and polyphosphate. An overall conversion of 57% of the substrates into 2′3′-cGAMP was achieved in relation to the initial guanosine concentration.

There are few reports on the direct epoxidation of propylene catalyzed by LaCoO₃ perovskite to form propylene oxide (PO) (both experimental and theoretical studies), especially the promoting effect of Cu doping. Herein, we report a comprehensive mechanistic study using both DFT calculations and microkinetic simulations for undoped and Cu-doped LaCoO₃(110)–Cl to explore the effects of Cu doping in LaCoO₃ perovskite towards PO selectivity. The propylene oxidation process consists of two parallel pathways, i.e., allylic hydrogen stripping and propylene oxametalcycle (OOMMP) intermediate mechanisms. Our results indicated that doping Cu has little effect on the selectivity for PO on LaCoO₃ without Cl due to its very low reactivity. Alternatively, in the presence of Cl, copper doping not only lowers the strength of the Brønsted base of molecular

In this study, we successfully synthesized a carbon-coated nickel phosphide composite catalyst (Ni₂P@C) through a strategy of polyvinylpyrrolidone (PVP)-assisted pyrolysis and phosphidation of Ni-MOF. Thorough structural characterization revealed that the assistance of PVP significantly decreased the size of the nickel nanoparticles during pyrolysis, and the subsequent gas phosphidation transformed the metallic nickel into the Ni₂P phase with strengthened Ni–P synergy. The resulting core–shell structured Ni₂P@C possessed a substantial number of surface Ni^{δ +} sites with electron deficiency, which served as both a metal center to dissociate hydrogen and a Lewis acid to activate the C–O bond. Remarkably, under mild reaction conditions (120 °C and p_{H 2} of 2.0 MPa), the Ni₂P@C composite demonstrated exceptional activity for hydrodeoxygenation of furfuryl alcohol, achieving an impressive 2-methylfuran productivity of 1.7 g_2-MF g_Cata⁻¹ h⁻¹. These results surpass the performance of most non-noble metal catalysts currently reported. This study could provide valuable insights for the rational design of advanced carbon-coated Ni₂P composite catalysts for hydrogenative biomass upgrading.

Sulfur undergoes various changes from solid S₈ to soluble lithium polysulfides (Li₂S₈–Li₂S₄) and insoluble Li₂S₂ and Li₂S during charge–discharge cycling of lithium sulfur (Li–S) batteries. The dissolution of sulfur-containing compounds in battery electrolytes and their movement between electrodes, known as the polysulfide shuttle effect, decreases the battery performance. In addition, the kinetics of sulfur redox reactions are sluggish. Different host materials have been explored to address these issues. Herein, nanofibres of conjugated polymers have been synthesised that have multiple electron transport pathways. The cross-linker is nickel phthalocyanine tetrasulfonic acid tetrasodium salt (NPTS). Sulfur is situated in the voids of cross-linked nanofibres of the polymer and Ni²⁺ present in NPTS attracts the negative charge-bearing polysulfides. Due to the confinement and polyvalent electrostatic attraction, the solubility of sulfur and polysulfide is suppressed. Density functional theory calculations revealed that S²⁻ interacts with Ni²⁺ and Li⁺ interacts with the pyrrolic nitrogens of PPy-NPTS. The overlap of the p-orbitals of sulfur and nickel is determined from the density of states calculations. The bond length of Li₂S is ideal for this interaction, hence this molecule showed the highest adsorption energy with the cross-linked polymeric host. The adsorption energy decreased upon an increase in the number of sulfur atoms in the polysulfide chain due to the bond length mismatch. However, due to electrostatic polyvalent interaction, the adsorption energy is sufficient to suppress polysulfide dissolution. Thus, the structure of this host material with nickel cations and pyrrolic nitrogens is suitable to adsorb lithium polysulfides irrespective of their length, unlike neutral hosts. This efficient binding also improved the electrocatalysis of the sulfur redox reaction. Hence, the Li–S battery containing these nanofibres showed a specific capacity of 1326 mA h g⁻¹ at 0.2C. Batteries fabricated considering practical parameters, such as low electrolyte to sulfur ratio of 5.0 μL mg⁻¹ with sulfur loading of 4.0 mg cm⁻², showed impressive performance.