Journal of Catalysis最新文献

Chemical looping H₂O splitting is considered as a promising approach to produce hydrogen thanks to its lower energy consumption and carbon footprint compared with traditional steam reforming. Fe-based oxides have been paid much attention but suffer from inferior H₂ production rate and stability due to insufficient activation for H₂O. Herein, it was found that the introduction of Cr into MgFe spinel oxides (MgFe_xCr_2-xO₄, MFCO) could greatly increase the performance of H₂O splitting driven by CH₄ reduction with the highest peak H₂ production rate of about 4.65 mmol min⁻¹ g⁻¹, H₂ productivity of about 2.88 mmol g⁻¹ and good stability during multiple redox cycles for MFCO-46 (the atomic ratio of Fe and Cr of 2:3), which exceeded most of the state-of-the-art Fe-based oxides. This originated from the Cr doping promoting Fe⁰ nanoparticles exsolution by activating CH₄ and Fe-O_v-Cr species formation which relay catalyzed H₂O splitting and was favorable for the fast recovery of lattice oxygen converted.

Ag is often studied as catalyst for electrochemical CO₂ reduction as it shows high selectivity towards CO and is easily alloyed with Cu to enhance performance using CuAg catalysts. In this study, we investigated the effect of temperature on Ag and CuAg catalysts and compare these with previous results on Au and Cu catalysts. We show that the temperature effect is complicated as it shows an interplay with CO₂ concentration, potential and mass transport. It is therefore crucial to deconvolute these parameters and study the effect of temperature under different conditions. Moreover, we show that alloying Ag with Cu can inhibit some of the deactivation effects observed at high temperatures on pure Cu. CuAg alloys can prevent the dominance of hydrogen evolution at elevated temperatures, although an optimum of C2+ products with temperature is still observed.

Direct conversion of methanol and acetic acid (HAc) into acrylic acid (AA) and methyl acrylate (MA) is remarkably significant for the high-value utilization of coal-based chemicals. However, the previous catalysts, due to their single function or poor synergy between multiple active sites, remain large challenges in direct synthesis of acrylic acid. Herein, we designed a novel catalyst system through coating TiO₂ to sodium superionic conductor (NASICON) substrate for direct synthesis of acrylic acid from methanol and acetic acid. It was revealed that the catalyst with TiO₂ coating showed obviously improved performance. The selectivity of AA+MA highly reached 56.1 % at 380 °C, corresponding to the spatiotemporal yield of 46.5 μmol·g⁻¹·min⁻¹. It was demonstrated that TiO₂ coating catalyzes the oxidative dehydrogenation of methanol to formaldehyde, while NASICON substrate exerts important effects on the aldol condensation of formaldehyde and acetic acid, and their effective synergy promotes the direct synthesis of acrylic acid.

Ni-based catalysts supported on delaminated ITQ-6 zeolite with different Si/Al ratios, 30 and ∞, were tested in the methanation of CO₂ and CO. ITQ-6 supports exhibited high surface areas (> 590 m²/g), and the catalysts based on them presented elevated CO₂ and CO conversion values, turnover frequencies (TOF), and CH₄ selectivity (> 90 %). Comparing the ITQ-6 catalyst and its precursor ferrierite (FER)-based catalyst, H₂-chemisorption results confirmed higher metallic dispersion for the former, which resulted in improved H₂ uptake and efficient interaction of reaction intermediates via the associative pathway. Combined kinetic studies indicated that their higher available metallic surface contributed to lower apparent activation energies towards CH₄ formation, accounting for the higher selectivity values. A 15 wt% Ni-based catalyst supported on ITQ-6 zeolite (Si/Al = 30) exhibited catalytic results (X_CO2 = 79 % y S_CH4 = 98 %) comparable or even superior to some of the best zeolite-based catalysts reported so far.

Constructing van der Waals (vdW) heterostructures is one of the effective strategies for developing highly efficient photocatalysts. In this study, we have designed a novel BTe/HfS₂ heterostructure and systematically investigated its electronic properties and photocatalytic performance using first-principles calculations. The dynamic stability and thermodynamic stability of the heterostructure are verified through phonon spectrum simulations and ab initio molecular dynamics (AIMD) simulations, respectively, enhancing the likelihood of experimental synthesis. The bandgap of the BTe/HfS₂ heterostructure is 0.12 eV, and the band edge positions satisfy the overall water splitting requirements for photocatalysts. The charge density difference, work function, Bader charge, and band alignment all confirm that the BTe/HfS₂ heterostructure is a typical direct Z-scheme heterostructure, effectively facilitating the separation of photogenerated charge carriers and exhibiting strong redox capability. The solar-to-hydrogen (STH) efficiency of the BTe/HfS₂ heterostructure reaches as high as 17.32 %. Moreover, the heterostructure exhibits strong light absorption capability, reaching a magnitude of 10⁵. The carrier mobility of the BTe/HfS₂ heterostructure surpasses that of two individual monolayer materials, with the hole mobility in the x-direction reaching an impressive 28357.15 cm²s^-1V^-1. Simultaneously, the Gibbs free energy indicates that the BTe/HfS₂ heterostructure can undergo the hydrogen evolution reaction (HER) with only 0.19 eV of external potential at pH = 0. Moreover, at pH = 7, it can spontaneously convert H₂O into O₂. Therefore, the newly designed BTe/HfS₂ heterostructure offers a new direction for practical applications of photocatalysts.

An efficient and straightforward procedure for the synthesis of HFIP esters-containing 2H-benzopyrans has been established through palladium-catalyzed one-pot cyclization/carbonylation reaction of substituted propargyl ethers with HFIP by using formic acid as the CO precursor. A diverse set of 2H-benzopyrans have been formed with HFIP esters as attractive functional groups in moderate to excellent yields. This protocol features broad substrate scopes and no manipulation of toxic CO gas.

The study of transition metals and various possible surface compositions has sparked great interest in low-cost materials, which exhibit high activity and selectivity in catalysis. While various single-atom catalysts loaded on transition metal dichalcogenide (TMD) substrates with excellent CO₂ reduction performance have been identified, the relationship between catalytic activity and the intrinsic properties of TMD single-atom catalysts remains unclear. Hence, a high-throughput first-principle computational approach is proposed to screen 24 transition metals anchored on 8 TMD monolayers to determine their catalytic activity in CO₂RR. The results show that Fe@CoS₂, Pt@TiTe₂ and Co@CoS₂ exhibit exceptional performances with low CO₂RR limiting-potentials of −0.045 eV, 0.75 eV, and 0.54 eV, respectively, showcasing selective pathways towards formic acid (HCOOH), methane (CH₄), and methanol (CH₃OH). Employing the Sure Independence Screening and Sparsifying Operator method(SISSO), key descriptors linking the performance of single-atom catalysts with their intrinsic features are identified, providing insights for the discovery of superior CO₂RR catalysts. Moreover, it was observed that a feature of the anchored single atom, the difference between covalent radius and atomic radius (CR-R), is associated with multiple crucial reaction steps, exhibiting a strong linear relationship with the charge transfer of *COOH. This work not only identifies promising CO₂RR catalysts but also establishes a predictive framework for screening catalysts based on their intrinsic properties, paving the way for future advancements in CO₂ reduction research.

The direct epoxidation of propylene to propylene oxide (PO) represents a unique feature of gold nanoparticle catalysts. Different amounts of vanadium were introduced into TS-1 using a hydrothermal method to give V-TS-1, and the effect of various vanadium loadings on the catalytic performance of Au/V-TS-1 was investigated in the epoxidation of propylene under different reaction conditions. The obtained characterization results indicate that the molecular sieve pore structure and crystalline phase structure of TS-1 were maintained after vanadium incorporation, and vanadium was incorporated into the molecular sieve framework. The introduction of an appropriate amount of vanadium resulted in the homogeneous dispersion of gold particles with a small average particle size, which facilitated the epoxidation reaction. When V was introduced into TS-1, the propylene conversion decreased under the condition of 10 % H₂ concentration (C₃H₆/H₂ = 1/1) in the reaction atmosphere, but the PO selectivity was maintained. Interestingly, when the H₂ concentration in the reaction atmosphere was lowered to 2 % (C₃H₆/H₂ = 3/1), the propylene conversion in Au/TS-1 was significantly decreased compared to 10 % H₂ concentration condition, while in Au/V-TS-1, the propylene conversion was maintained in 2 % H₂ concentration condition compared to 10 % H₂. Au/V-TS-1 also maintained its selectivity for PO even when the H₂ concentration was lowered. Therefore, under low hydrogen concentration conditions, the PO formation rate of Au/V-TS-1 was much higher than that of Au/TS-1. More, the same trend was observed when Mo was added in place of V. Our strategy will guide the design of future catalysts as a way to utilize hydrogen more effectively while maintaining PO productivity.

A stabile and recyclable photocatalyst IL-TX was designed and synthesized by introducing the dye photocatalyst thioxanthenone into ionic liquids and its excellent photocatalytic performance was demonstrated by photophysical and electronic performance tests. The IL-TX was applied as a recyclable photocatalyst for α-cyanidation reaction of aromatic tertiary amines in MeOH at room temperature under blue light irradiation, and a range of cyanide products were obtained in good to excellent yields. Furthermore, the practicality of this protocol was further demonstrated through the optimization of the synthesis of the drug praziquantel and the natural product 8-oxopseudopalmatine. This study provides a greener and sustainable solution for photocatalytic cyanation reaction.

The selective hydrogenation of furfural derived from biomass is of significant importance in the synthesis of valuable chemical compounds. In this work, Cu-Ni bimetallic catalysts with varying metal ratios were effectively synthesized using the urea deposition method and employed in catalytic hydrogenation of furfural (FA) to furfuryl alcohol (FOL) and cyclopentanone (CPO) in different solvents. The study revealed that the synergistic interaction between Cu and Ni favors the formation of CuNi alloys, thereby facilitating the reduction of CuO and NiO and resulting in larger amount of metallic species (Cu^0/+ and Ni⁰), and promoting the formation of highly dispersed nanoparticles. Moreover, the formed Cu⁺ species can serve as Lewis acid sites and improve the adsorption of polarized C = O, thus significantly enhancing the selectivity to FOL. More importantly, the cooperation between Cu⁺ species and water can promote the aqueous-phase hydrogenation-rearrangement (AP-HR) of FA to CPO. Also, in-situ/on-line DRIFTS shows that Cu₃Ni₁/SiO₂ preferentially adsorbs and activates C = O and prefers to form 4-hydroxy-2-cyclopentenone (HCP), which is the key intermediate to form CPO. DFT calculations agree with the in-situ/on-line DRIFTS, showing that Cu₃Ni₁ (1 1 1) crystal surface with the lowest d-band center and the strongest electronic effects presents the highest adsorption energies of H₂, H₂O, and FA, the lowest adsorption energies of H*, FOL, and CPO, and the lowest energy barriers of Piancatelli rearrangement of FOL to HCP. Under the optimum conditions, Cu₃Ni₁/SiO₂ gives 99.9 % yield to FOL at 333 K in isopropanol and 96.7 % yield to CPO at 413 K in water. The low cost and high activity of Cu₃Ni₁/SiO₂ make it a potential catalyst for the green production of FOL and CPO in industry.