Applied Catalysis A: General最新文献

The introduction of oxygen vacancies (OVs) into photocatalysts has proven to be a successful tactic to boost CO₂ reduction. However, the challenge lies in acquiring OV sites that are stable in the long term, highly dispersed, and tunable in concentration. Herein, an innovative configuration, referred to as N-Bi^(3+x)+--O_V, was developed for the model semiconductor Bi₂O₂CO₃ via an in situ anion doping approach. The structure enables the synthetic photocatalyst to exhibit superb CO₂ photoreduction performance, with approximately 100% CO selectivity and remarkable long-term stability. Experimental studies and density functional theory (DFT) calculations show that replacing O^2- with N^3- uniformly in the [Bi₂O₂]²⁺ structural unit increases the chemical valence of Bi, elongates nearby Bi─O bonds, releases lattice O, improves CO₂ absorption, and decreases the energy barrier for the formation of the critical intermediate *COOH. This study offers new insights and potential opportunities for the development of reliable defect-type semiconductors and their catalytic applications.

BaTaO₂N (BTON) with a generous adsorption edge of ca. 660 nm and high theoretical solar-to-hydrogen conversion efficiency of ca. 20.6% has been extensively investigated for photocatalytic water splitting. In this study, we have successfully prepared a porous BTON nanosheet via employing Ba₂Bi₃Ta₂O₁₁Cl (BBTOC) oxyhalide as a novel nitridation precursor. The oxygen evolution rate of the BTON nanosheet is 108 μmol·h⁻¹, which is three times higher than that of BTON (25.9 μmol·h⁻¹) prepared by conventional solid-state method. The successful construction of porous BTON nanosheet is due to the structural transformation of BBTOC nanosheet precursor and facile evaporation of Bi and Cl elements. The porous nanosheet morphology of BTON can not only promote the transfer of photogenerated charge carriers but also provide abundant reaction sites for the oxygen evolution reaction. This work demonstrates a novel and efficient strategy for preparing oxynitride for efficient solar energy conversion.

The geometric and electronic structure of Pt active sites plays a crucial role in determining the catalysts performance, but precise regulation remains challenging. Herein, we propose a novel approach to modulate the nature of Pt active sites by combining photo-deposition of Pt nanoparticles with ultra-low Mo loading (0.1 wt%) modification on Pt/SiO₂ catalysts. The addition of ultra-low loading Mo promoter not only effectively reduces the size of Pt particles but also donates electrons to the Pt particles. Furthermore, the photo-deposited Pt particles exhibit a higher proportion of metallic Pt species, which is more stable than that metallic Pt species obtained by H₂ reduction, compared to those prepared using traditional wetness impregnation methods. Propane oxidation activity evaluations confirm that the photo-deposited and Mo-modified Pt/0.1Mo/SiO₂-P catalyst exhibits the highest activity among all the prepared catalysts. Combined with experiments of C₃H₈-TPSR and in-situ DRIFT spectra of propane oxidation, it is found that the Pt/0.1Mo/SiO₂-P catalyst remarkably promotes propane activation and C-H bond cleavage due to the nature change of Pt active sites, and the presence of gaseous oxygen benefits propane cleavage on active sites. Our primary results provide a promising strategy for designing superior platinum catalysts by regulating Pt active sites nature for efficient propane complete oxidation.

Metal-organic framework (MOF)-derived hollow metal oxides exhibit significant potential as cutting-edge electrocatalysts for the oxygen evolution reaction (OER) owing to their exceptional intrinsic activity, expansive specific surface area, structured controllability, and adjustable pore dimensions. Nevertheless, their industrial utilization faces the obstacles such as intricate synthesis procedures, limited scalability, and inconsistent performance, necessitating the formulation of effective solutions. Various engineering strategies have been proposed by researchers to tackle these hurdles. This comprehensive review highlights recent breakthroughs in engineering MOF-derived hollow metal oxides and their applications in electrocatalytic OER. It initiates by juxtaposing the drawbacks of traditional metal oxides against the advantages of MOF-derived hollow metal oxides. Subsequently, it delves into a thorough exploration of the engineering methodologies employed to elevate their OER efficiency. Lastly, the review delineates current challenges and potential avenues for the development of more efficient MOF-derived hollow metal oxide electrocatalysts in the future.

Hydroconversion of guaiacol (GUA) over γ-Al₂O₃ and phosphatized-γ-Al₂O₃ (γ-Al₂O₃(P)) supported Ni catalysts was initiated by Lewis-sites and active Ni sites. Conversion proceeded via transmethylation and hydrodemethylation/hydrodemethoxylation as major and minor pathways, respectively, resulting in mainly catechol and methylcatechols, and via series of consecutive hydrodehydroxylation (HDHY) and ring hydrogenation (HYD) reactions leading to partially and fully deoxygenated, saturated, and unsaturated products. High Ni-loading and high H₂ pressure promoted the formation of cyclohexane and methyl-substituted cyclohexanes; however, above 300 °C the hydrogenation–dehydrogenation equilibrium favored the formation of benzene and methyl-substituted benzenes. Ni/γ-Al₂O₃(P) showed suppressed HYD/HDHY activity resulting in pronounced formation of catechol and/or phenol and their methyl-substituted derivatives. Surface phenolate species were substantiated as surface intermediates of hydrodeoxygenation. Phosphatizing reduced the concentration of both basic OH and Lewis acid (Al⁺) – Lewis base (O^–) pair surface sites of the γ-Al₂O₃ support and, thereby, suppressed phenolate formation and hydrodeoxgenation.

In this study, we report an efficient, stable, and renewable N, P co-doped coffee biochar-based catalyst loaded with highly dispersed Ni-N_x species (Ni/NPCB-600), and it was successfully applied to the aqueous-phase chemoselective reduction or reductive amination of diverse nitroarenes (Yield up to >91%). Experimental and characterization studies revealed that N, P co-doping have a synergistic effect on improving the catalytic performance of Ni/NPCB-600. The textural properties of Ni/NPCB-600 are enhanced after doping of P, which can facilitate mass transfer and expose more accessible active sites in the reaction. The doping of N could induce the formation of Ni-N_x sites and enhance the basicity of the Ni/NPCB-600 catalyst, which can promote the adsorption and activation of formic acid and nitroarenes, respectively. This is the first example of N, P co-doped coffee biochar-based catalyst for nitroarenes reduction or reductive amination, and reveals its potential industrial application prospects.

Dry reforming of methane (DRM) provides a desired approach to produce valuable syngas in tackling greenhouse gases. Yet it faces a formidable challenge in the design and synthesis of high coke-resistant Ni-based catalysts. Herein, we report a nanoreactor strategy to construct a supported Ni catalyst (Ni@SiO₂@SiO₂) for reinforcing coke-resistance during DRM, by effectively encapsulating small Ni nanoparticles into dendritic fibrous silica (SiO₂) nanospheres and coating SiO₂ shell layers. Taking advantage of chemical characteristics of citric acid (CA), CA-chelated Ni impregnation enables the uniform immobilization of Ni species into the radial SiO₂ framework, then following carbonization produces protective carbon layers on the Ni nanoparticle surface during SiO₂ coating, which can be removed via oxidizing calcination. The resultant pomegranate-like nanoreactor catalyst possesses outstanding coke-resistance, without any detectable coke deposition after 200 h of DRM reaction at 700 ℃, benefiting from effectively restricting metal sintering and fully preventing formation of inert carbon species.

Being activated by methylalumoxane ([Al]/[Zr] = 10), (η⁵-C₅H₅)₂ZrCl₂ (Zr1) and [(η⁵-C₅H₄SiMe₂)₂O]ZrCl₂ (Zr2) catalyze selective dimerization of α-olefins with low productivity (turnover number TON ∼2000). Our previous research of heterocycle-fused ansa-zirconocenes revealed that SiMe₂-bridged complexes catalyze polymerization of α-olefins, whereas CH₂CH₂-bridged complexes are high-performance oligomerization catalysts (TON ∼ 4∙10⁵). We proposed that further elongation of the bridge will allow obtaining dimerization catalysts. New –SiMe₂OSiMe₂– bridged ansa-zirconocenes Zr3–Zr11 were synthesized and studied in oct-1-ene dimerization at 100 °C and [oct-1-ene]/[Zr] ratio of 3∙10⁴. In the absence of H₂ bis(5,6-dihydroindeno[2,1-b]indole) derivatives Zr8 and Zr9 demonstrated high activity and dimerization selectivity up to 94%. In the presence of H₂ symmetrical indenoindole complexes Zr5–Zr9 appeared to be even more active, but up to 24% of hydrogenated oct-1-ene dimer HC16 was formed. Mixed-ligand complexes Zr10 and Zr11 catalyzed oct-1-ene dimerization with up to 99% selectivity without the formation of HC16 even in trace amounts.

The co-hydroprocessing of lignite and heavy residue generates a substantial amount of tail oil, compromising the technical efficiency and posing significant environmental hazards. We proposed a cascade utilization scheme via the combination of tail-oil cycling and tail-oil co-hydrocracking, to maximize the utilization of catalytic components and enhance the conversion of heavy feedstock. At a cycling ratio of 50 wt%, the conversion efficiency of carbonaceous solids increased from 88 % to over 95 % after 5 cycles. The effluent tail oil also represented a favorable hydrocracking performance when mixed with Merey atmospheric residue. The spent catalysts and iron-containing minerals gradually accumulated in solid residues, which provided additional catalytic components for hydrogenation and coke inhibition in the co-hydroprocessing and co-hydrocracking systems. Moreover, the cycling process improved the colloidal stability and enhanced the hydrogenolysis of heavy components, effectively curbing the degradation tendency within the reaction system and producing more light oils.

The crystallinity and morphology of the zeolites have a significant effect on their catalytic performance. Herein, the influence of the introduced metal and copolymer in the synthesis gel on the crystallinity and morphology of the synthesized M-ETS-10 (M=Fe, Co, Ni, Cu) zeolites and on their catalytic activity were investigated. The crystallinity (110%) of the M-ETS-10 (M=Fe, Co, Ni, Cu) was enhanced; the morphology of Fe(or Co)-ETS-10 was changed to imperfect tetragonal bipyramidal shapes, and Ni(or Cu)-ETS-10 turned into irregular large particles consisted of defective tetragonal bipyramidal. Incorporating copolymer into the gel contributed to all the hierarchical M-ETS-10-H being present multi-layered structure consisted of nanosheets. The hierarchical Cu-ETS-10-H exhibited superior catalytic activity than M-ETS-10-H and Cu-ETS-10 in the C–C bond cleavage and decarboxylative hydrosulfonylation reactions. This was attributed to the presence of Lewis basic sites, reversible transformation of Cu²⁺ to Cu⁺, as well as the hierarchical pore structure.