查看更多>>摘要：Photocatalytic reductive coupling of carbon-carbon bond to assemble complex molecular frameworks holds the great promising for solar energy storage and value-added chemicals production. This process generally demands noble-photosensitizer or powered by ultraviolet light, along with harsh conditions, which inevitably induces undesired by-product with poor selectivity. Here, we demonstrated selectively reductive aromatic ketones into pinacol on low-cost photocatalysts Ni-doped quantum dots, in which the yield can reach up to 88% with ketones conversion more than 95% under visible-light irradiation for 5 h. A novel mechanism dedicated to the interaction between in situ generated oxidized sacrificial agents TEA(.+) and reactants for key ketyl radical formation via proton-coupled electron transfer (PCET) is elaborately probed by EPR measurement, iotope labeling experiments and DFT calculation. This work emerges a new family of catalysts for C-C coupling by solar energy. More importantly, it provides more credible demonstration for TEA activated photocatalytic conversion in organic synthesis.
查看更多>>摘要：Atomic-level insight into the unique catalytic capability of single-atom catalysts that distinguished from nanometer-sized counterparts is highly desirable for catalyst design and catalysis research. By synthesizing single Pd atoms supported on TiO2 as a catalyst, here we demonstrate a steric hindrance effect of single atoms induced by the unique isolation of single-atom active sites to achieve a remarkable enhancement on catalytic performance in the synthesis of dimethyl carbonate. Experimental results and density functional theory calculations reveal that such steric hindrance effect of single atoms favors the yield of the desired product dimethyl carbonate against further reacting with intermediates to form byproduct, because no extra Pd species around single Pd atoms provide active sites to further adsorb and activate substrates directly. The discovery of such steric hindrance effect is a valuable supplement to single-atom catalysis, and may promote single-atom catalysts to be widely applied in selective catalytic reactions.
Kim, PaulVan Der Mynsbrugge, JeroenAljama, HassanLardinois, Trevor M....
13页
查看更多>>摘要：This study investigates NO adsorption on Pd-exchanged chabazite (Pd/H-CHA), a promising passive NOx adsorber (PNA) for capturing cold-start NOx emissions of gasoline-and diesel-powered vehicles. Temperature programed desorption (TPD) and IR spectroscopy are combined with theoretical calculations to elucidate how and where NO is stored, and how water and O-2 affect this process. NO adsorption on Pd/H-CHA produces two TPD features, around 423 and 753 K, and IR bands centered at 1860 and 1810 cm(-1). Calculated NO stretching frequencies and maximum-desorption temperatures reveal that Pd2+ and Pd+ sites are responsible for these low and high-temperature features, respectively, and that while the IR feature at 1810 cm(-1) is due to NO adsorption on Pd+, the 1860 cm(-1) feature contains contributions from both weakly-bound NO on Pd2+ and more strongly bound NO on Pd+, consistent with experimentally observed effects of water and O-2.
查看更多>>摘要：The tandem reactions of CO2-assisted oxidative dehydrogenation and aromatization (CO2-ODA) of ethane were investigated over ZSM-5 modified with zinc (Zn) and phosphorus (P) by experimental studies and DFT calculations. The nature of active Zn species and their interaction with P were elucidated for understanding Zn/P-ZSM5 catalyzed CO2-ODA reaction of ethane. Compared to the direct dehydrogenation and aromatization (DDA) reaction, the Zn/P-ZSM-5 catalyst possessed higher ethane conversion, enhanced aromatics yield, and better stability in the CO2-ODA reaction. The presence of CO2 reduced the carbon deposition, stabilized the Zn species, and thereby facilitated the generation of more liquid aromatics in CO2-assisted ethane aromatization. In situ characterization and DFT calculations provided insight into the mechanisms of CO2-ODA over the Zn/P-ZSM-5 catalyst.
查看更多>>摘要：Optimizing the electronic structure of the electrocatalyst to adjust the adsorption energies of oxygen intermediates to approach the equilibrium potential (U-RHE(0) = 1.23 V) is of paramount importance to inhibit the sluggish reaction kinetics of the oxygen reduction/oxygen evolution reaction (ORR/OER), yet remains a huge challenge. Herein, a hierarchical 1D/3D hollow carbon nanopolyhedron with strong electron coupling between the encapsulated CoNi alloy and Co-Nx sites in N-CNTs was designed by a silicon protection-Ni infiltration strategy. Impressively, the optimized CoNi/Co-N@HNC catalyst exhibits high oxygen catalytic activity with a small potential gap of 0.73 V and superior ZABs durability over 350 h. DFT simulation results revealed that coupling with CoNi nanoclusters can effectively downshift the Ed energy levels of the Co adsorption site in CoN4, dramatically decreased the energy barrier of the rate-determining step (OH* to OH- in ORR; OH* to O* in OER), thereby promote the overall oxygen catalysis reaction kinetics.
查看更多>>摘要：Cu3P nanoparticles (NPs) were proposed as an efficient antibacterial agent for impeding bacterial resistance. Both sensitive and resistant strains of E. coli and S. aureus (3 x 106 CFU mL-1), and the microbial populations from a fishery water were completely inactivated by Cu3P NPs (<= 1.5 mu g mL-1) within 30 min with no regrowth. The antibacterial mechanism of Cu3P NPs relied on their own multiple enzyme-like activities, to elucidate, the action of ROS produced by their oxidase- and peroxidase- like activities was facilitated by their inherent activities for glutathione depletion and the lipid peroxidation. Comparing with that traditional antibiotics induced bacterial resistance (6 out of 7) within 3 passages, Cu3P NPs kept their initially inactivated efficiency, demonstrating that they can delay the onset of bacterial resistance. Furthermore, the Cu3P NPs shown no obviously toxic effect on aquatic organisms and a negligible side-effect toward mammalian tissues. This strategy is insightful for struggle with resistant bacteria.
查看更多>>摘要：This study was conducted to investigate the effect of reducing pretreatment on physicochemical properties of zeolite catalysts and their performances on formaldehyde (HCHO) oxidation at ambient temperature. Pd/TS-1 (Fresh) was tailored by different reductive gases (H-2, CO) and liquid agents [ascorbic acid (AA), ethylene glycol (EG), sodium borohydride (NaBH4)]. Based on the characterization of HRTEM and CO chemisorption, it was shown that the reducing treatment could significantly reduce the size of Pd nanoparticles (NPs) based on the good dispersion of noble metal. The smallest size of Pd nanoparticles with 5.1 nm was achieved by using NaBH4 as reducing agent. Accordingly, the best activity was observed on the Pd/TS-1(NaBH4) sample, pretreated by NaBH4 in aqueous solution, which could eliminate HCHO completely even at room temperature. Combined with Raman, H-2-TPR, and CO-DRIFT, the excellent catalytic performance of Pd/TS-1(NaBH4) are mainly ascribed to the high Pd dispersion, superior redox properties and abundant active O-2 species.
Ibraheem, ShumailaYasin, GhulamKumar, AnujMushtaq, Muhammad Asim...
10页
查看更多>>摘要：Water-electrolysis intends a favorable green technology to hold the worldwide energy and ecological disaster, but its efficacy is significantly restricted by the slow reaction kinetics of both the anodic oxygen evolution reaction (OER) and cathodic hydrogen evolution reaction (HER). Herein, the fabrication of multi-cation incorporated Fe2+/3+/Co2+ species into selenides nanorods (Fe@Co/Se-2-NRs) and corresponding analysis of their catalytic activity for electrochemical (EC) and solar-driven water splitting as a purpose of the composition are reported. This efficient approach can fabulously endow electronic structure modulation and the direct evidence of electron-transfer-route between transition-metals and selenides, which are vital to improving the electrocatalytic activity, has never been confirmed before. For the first time, we explored the electron-transfer route of intensely-coupled Fe@Co/Se-2-NRs catalyst, in which the Fe2+/3+/Co2+ species strongly-coupled to selenide through the Fe-coordinated Co-bridged-bond. Finally, density functional theory calculations disclose that the multi-cation doping effects into selenides are vital for enhanced electrocatalytic performance.
查看更多>>摘要：WO3 as a photoanode has the disadvantage of poor charge separation and low solar utilization. It is necessary to surmount these weaknesses to improve its performance. In this work, we doped FeOOH with F to prepare F: FeOOH/BiVO4/WO3 photoanode by the facile method. According to the photoelectrochemical evaluation, in the phosphate buffer electrolyte, the maximum photocurrent of the composite photoanode (3.1 mA/cm(2)) is 7 times and 9 times that of WO3 and BiVO4, respectively. The improvement is ascribable to F:FeOOH can extract holes and improve charge transfer. Compared with BiVO4/WO3 and original components, F:FeOOH/BiVO4/WO3 photoanode enhances charge separation and also shows good stability and electrons lifetime. Additionally, F -doped FeOOH has better OER catalytic performance than FeOOH according to theoretical calculation, which is consistent with experimental results. This work might extend application of cocatalyst in decomposition PEC water splitting.
查看更多>>摘要：Siloxene features abundant functional groups and oxygen vacancies, which facilitates the ultrafine platinum nanoparticles loading for catalyzing hydrogen evolution reaction (HER). Herein, a siloxene-p-Pt-2 h composite has been fabricated with an ultralow platinum loading on siloxene (0.56 wt%), which shows greatly enhanced HER activity featuring an ultralow overpotential (eta(10) = 23 mV). Attractively, the siloxene-p-Pt-2 h has been applied as a HER catalyst in a Zn-H2O fuel cell, demonstrating a high power density of 157 mW cm(-2) in coupling with the cathode hydrogen evolution. Moreover, a coupled configuration between two Zn-H2O fuel cells in series and the cell-powered hydroxide electrolyzer achieves the efficient hydrogen co-productions co-catalyzed by the HER catalysts. The excellent HER performance is attributed to the hydrophilic character and the optimal Gibbs free energy via the strong interaction between the siloxene and platinum nanoparticles. This work provides a novel design of self-powered co-productions of hydrogen.
NSTL
Elsevier