查看更多>>摘要：Toluene, as one of the representative biomass tar model compound, has been widely chosen for investigation of biomass tar reforming. Herein, novel Ni/(Mg, Al)O-x (Ni/MAO) catalysts derived from Ni-Mg-Al hydrotalcites were prepared successfully and used for steam reforming of toluene (SRT). Among all the catalysts, Ni/MAO catalyst prepared at pH of 10 and aging temperature of 20 degrees C (Ni/MAO-10) exhibited superior activity in toluene conversion (95.3%) and syngas production (833 mmol/g-Ni), as well as the excellent resistance to carbon deposition. Through characterizations, the highest basicity, highest reducibility, tailored "rosette-like" morphology, and larger specific surface area in Ni/MAO-10 were confirmed. Furthermore, the structure-activity relationship, reforming mechanism, deactivation, and regeneration of the catalyst were comprehensively elaborated from rigorous experiments, and meanwhile, the activation energies and turnover frequency (TOF) values of four Ni/MAO catalysts in SRT were calculated to theoretically explain their activities.
查看更多>>摘要：Natural chalcopyrite (NCP) was used as a low-cost and efficient activator of peroxymonosulfate (PMS) to repair groundwater polluted by aged landfill leachate. The optimal remediation effect of polluted groundwater was achieved at pH 8, PMS concentration 25 mM and NCP dosage 10 g/L via response surface method. The excellent performance of NCP was mainly Fe3+/Fe2+ and Cu2+/Cu+ cycles promoted by sulfur species, which was investigated via XPS analysis. Furthermore, the transformation of SO4 center dot, center dot OH and O2 center dot were clarified by quenching experiments and ESR. The conversion of organics was revealed by UV-vis spectra and threedimensional fluorescence spectra. Moreover, the toxicity of polluted groundwater after remediation was significantly reduced through the growth of Chlorella pyrenoidosa. Finally, the flowing experiment using NCP/ sand column showed that NCP could effectively activate PMS and thereby restore polluted groundwater.
查看更多>>摘要：The synergistic effect in a bimetallic oxide usually plays a vital role in determining the behavior of supported-metal catalysts. We show the unique synergy in a SnxMn1Oy oxide, which can boost the hydrogenation catalysis of supported Pt nanoparticles for selective conversion of levulinic acid (LA) to gamma-valerolactone (GVL). On a series of Pt/SnxMn1Oy catalysts with a similar Pt loading (ca. 0.44 wt%) and a controlled Pt size (ca. 2.7 nm), the intrinsic TOF presents a volcano-like dependence on Pt-0 sites and Lewis acidity, which is determined by the variable synergistic effect between MnOy and SnOy. The optimal Pt/Sn0.8Mn1Oy catalyst exhibits a high iTOF of 2709 h(-1) and achieves 100% selectivity to GVL at 99% conversion of LA at 120 degrees C and 2 MPa of H-2. DFT calculations demonstrate that the incorporation of Sn can provide a lower energy barrier for the crucial elementary reactions.
查看更多>>摘要：Lactide, a crucial precursor of the bioplastic polylactic acid, was obtained through the gas-phase transesterification of alkyl lactates using a 5 wt% TiO2/SiO2 catalyst as an alternative to the conventional liquid-phase process. Lactide selectivity above 80% was achieved at 220 degrees C but conversion was thermodynamically limited at around 50% for all alkyl lactates. The nature of the ester alkyl chain had minimal impact of the thermodynamics of the reaction, but significantly influenced its kinetics. The Taft equation indicated that this kinetic effect was due to the polarity of the alkyl chain. Mechanistic studies indicated that lactide formed via a Langmuir-Hinshelwood mechanism involving two lactate molecules. The derived kinetic expression was fitted to experimental data of methyl lactate transesterification, resulting in a reduced chi-squared of 0.99 and an activation energy of 89.8 kJ.mol(-1). Initial rate kinetics confirmed that the proposed mechanism was valid for other alkyl lactate species.
查看更多>>摘要：CO2 activation is a vital knot for CO2-mediated energy conversion and storage. Frustrated Lewis pairs (FLPs) are well confirmed to be highly efficient in CO2 activation. Here, we synthesized the single-crystal ZnSn(OH)(6) cube with exposed (100) facet (Sc) and ZnSn(OH)(6) octahedra with exposed (111) facet (So) and created FLPs with different acid-base distance on these exposed facets by vacuum irradiation, resulting from the light unstability of terminal hydroxyls. Our results demonstrated that the FLPs with short acid-base distance on So are more efficient activation centers due to the strong orbital interactions, well exemplifying that shortening the Lewis acid-base distance is a potential route to develop highly efficient FLPs catalysts. In addition, as an initial attempt, the combination effects between facet junction separating charges and FLPs activating molecules were proposed to accelerate CO2 reduction. Our findings may provide new insights into designing photocatalysts with highly catalytic performances.
查看更多>>摘要：Electrochemical reduction of carbon dioxide (CO2ERR) provides a promising method for managing global carbon balance by transforming CO2 into green chemicals. However, the development of efficient electrocatalysts for the fast and selective CO2 reduction is still a big challenge. Herein we report a study on CO2ERR electrocatalytic activity of amino-substituted Co porphyrin (CoTAP) as a function of its immobilization mode. It is demonstrated that the covalently grafted complex CoTAP-cov exhibits a turnover frequency to CO formation (TOFco) of 6.0 s(-1) and the Faradic efficiency to CO (FEco) of similar to 100% at the overpotential of 550 mV making it one of the best catalysts to date. In contrast, noncovalently immobilized counterpart CoTAP-noncov shows a more moderate TOFco of 2.3 s(-1) and lower FEco of 85%. Our results demonstrate that the presence of the donating -NH2 groups within the lateral aromatic moiety is required to maximize the activity of the complex in CO2ERR. In turn, covalent grafting both mitigates the aggregation of the porphyrin catalyst and enhances the interfacial electron delivery rate. The combination of these factors furnishes a catalyst with an excellent intrinsic TOFco as high as 36.6 s(-1).
查看更多>>摘要：Constructing an electrocatalyst with highly durable active and cost-effective core-shell with a porous carbon nanosheet for the development of high efficiency energy conversion and storage devices. Herein, we developed core-shell nickel-iron oxide on a highly porous N-doped carbon nanosheet (CS-NFO@PNC) via a facile solvothermal calcination route. The optimized CS-NFO@PNC-700 showed remarkable electrocatalytic activity towards ORR (0.85 V vs RHE), OER r10 = 217 mV, and HER r10 = 200 mV with excellent durability towards the corresponding half-cell reactions. Further, we investigated the ORR, OER, and HER mechanistic pathways of the electrocatalyst using the density functional theory. Finally, we fabricated a rechargeable liquid electrolyte-based zinc-air battery with CS-NFO@PNC-700 as the cathode which displayed an improved power density of 130 mW cm-2 at 217 mA cm-2 with excellent durability of 180 h. The rechargeable flexible quasi-solid-state zinc-air battery with CS-NFO@PNC-700 air cathode, which exhibited excellent long term durability over 40 h at 5 mA cm- 2.
查看更多>>摘要：The conventional water electrolysis system is seriously restricted by the sluggish kinetics of anodic oxygen evolution reaction. Electroreforming of organic substances coupling with electrochemical hydrogen evolution is an innovative strategy to achieve energy-saving co-generation of value-added chemicals and hydrogen. Herein, NiIr-based metal-organic framework (MOF) nanosheet arrays are in situ grown on Ni foam (NiIr-MOF/NF) and employed as a bifunctional self-supported electrocatalyst to oxidize small organic molecules of methanol to the value-added chemical formate while efficiently facilitating hydrogen production. The constructed co-electrolytic system based on HER-methanol oxidation reaction (MOR) bifunctional NiIr-MOF/NF electrocatalyst possesses ultra-high energy conversion efficiency for electrochemically assisted overall water splitting, with a low cell voltage of only 1.39 V to achieve the current density of 10 mA cm(-2). Especially, the Faradaic efficiencies of the cathode and anode could both reach nearly 100% for H-2 and formate generated in 1 M KOH containing 4 M methanol.
查看更多>>摘要：We develop a new PdCu/UTCN hybrid by loading low-crystalline PdCu NPs on large-area ultrathin 2D carbon nitride (UTCN) nanosheets that exfoliated from bulk g-C3N4 using a twice thermal exfoliation and repolymerization method for photocatalytic Suzuki C-C cross coupling reaction. Due to the advantages of 2D structure of the UTCN and the changes in electronic structure and surface structure of low-crystalline PdCu NPs, PdCu/UTCN shows promoted photocatalytic activity with high selectivity for Suzuki coupling reaction. The TOF value for coupling of iodobenzene with phenylboronic acid is 418.2 h-1, which is 8 and 6.2 times higher than that of previously reported Pd-g-C3N4 and Pd based alloy photocatalysts under the same reaction, respectively. Morevoer, this photocatalyst shows a good functional group tolerance as well as good to excellent yield and selectivity for various substrates. This study reports for the first time the PdCu alloy supported UTCN photocatalytic material for enhanced Suzuki reaction.
查看更多>>摘要：The Si/MoSx photocathode is usually fabricated by electrochemical deposition, which high interfacial resistance is usually solved by building a buried junction or inserting a metal layer between Si and MoSx. Both methods, however, involve toxic gas sources or harsh conditions of high pressure. Here, a green and mild route has been designed to insert the N-doped carbon (CN) layer between Si and MoSx by in situ polymerization and postannealing, which improves the transfer of interfacial carriers and avoids unnecessary absorption of incident light by itself. Meanwhile, combining two-step wet etching and photo-assisted electro-deposition, the Si-PN/CN/MoSx photocathode with antireflective structure was obtained.
NSTL
Elsevier