查看更多>>摘要：Coupling hydrogen fuel production with selective oxidative organic synthesis in one cooperative manner offers a promising avenue to enable efficient utilization of photoexcited carriers to achieve sustainable chemistry. Herein, a new Mo2N/Mn0.3Cd0.7S/CoPi photocatalyst is reported for visible-light-driven hydrogen production paired with selectively oxidative C-C bond formation. Mo2N acting as electron collectors and reduction sites are adsorbed on the Mn0.3Cd0.7S by interfacial Mo-S bond, while CoPi acting as hole collectors and active sites for oxidation reaction are deposited on Mo2N/Mn0.3Cd0.7S. Remarkably, the synergetic effect of Mo2N and CoPi dual cocatalysts results in the adjustable flexibility of switching benzaldehyde (BAD) production to C-C coupling synthesis, thus exhibiting the high selectivity of C-C coupling products. Mechanism studies indicate that the C-C-Coupling reaction occurs through a free radical mechanism. The present work gives insight for achieving highly efficient C-C coupling synthesis with hydrogen evolution by loading dual cocatalysts.
查看更多>>摘要：Covalent organic nanosheets can be applied potentially to solar-to-hydrogen fuel conversion because of their long-range ordered structure and predictable regulation. Additionally, minor progress has been made in the precise synthesis of copper-loaded composite catalysts at the atomic level. Hence, we synthesized hybrid Cu@TpTG-iCON materials by anchoring copper(II) ions into the evenly dispersed tridentate chelation sites of the TpTG-iCON precursor, which maximized the exposure of active sites during the catalytic reaction. Taking advantage of the well-defined structural configuration and nanosheet morphology, the heterogeneous Cu@TpTGiCON catalyst exhibited an excellent hydrogen evolution reaction (HER) rate and significant stability in a ternary photocatalytic system. The atomic-level coordination modulation strategy in the covalent organic nanosheet matrix successfully demonstrated here has made possible the synthesis of other non-precious metal-based hybrid materials, indicating a step forward in the generation of a recyclable and efficient HER catalyst.
查看更多>>摘要：Efficient photocatalytic activity is always pressingly expected for photocatalytic technology on removing organic water contaminations. Modulating the intrinsic electronic properties is one of the most effective approaches to improve photocatalytic efficiency. Herein, we developed a promising photocatalyst through modulation electronic properties of iron-based metal organic framework by sulfur (S-MIL-53(Fe)), in which the sulfur particles were intramolecularly in-suite inserted into MIL-53(Fe) through annealing treatment process. The constructed S3-MIL-53(Fe) crystal with regular spindle-shaped polyhedron morphology exhibited superior higher apparent quantum efficiency (AQE) of 27.82% which was over 30 times than that of pure MIL-53(Fe) (0.903%) indicating the significantly enhanced photoactivity. A computational study was conducted to reveal the electronic structure changes and the resulted charge transfer induced by the sulfur modulation. The experimental and computational analyses suggest that intramolecular modulation MIL-53(Fe) with sulfur to engineer band structure for promoting charge transfer is a promising approach to improve the photocatalytic efficiency.
查看更多>>摘要：A photocatalyst of layered structural BiOBr doped with sulfur (S-BiOBr) was synthesized using a facile hydrothermal method. X-ray powder diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and density functional theory calculation revealed that S-BiOBr consisted of covalent [Bi2O2S](2+) layer and exchangeable bromide ions [Br-2](2-). The specific layered structure of S-BiOBr exhibited excellent performance for the intercalation, adsorption and photocatalytic degradation of ciprofloxacin (CIP) by forming interlayer [Bi2O2S](2+)--OOC-R complexes. Furthermore, the internal electric field enhanced by polarization effects in the [Bi2O2S](2+) layer was conducive to a lasting electron transfer in the dark condition after photoactivation. The electron of R-center dot radical derived from oxidizing [Bi2O2S]-OOC-R persistently migrated to the S-BiOBr surface and was trapped by O-2 to form O-2(center dot-), facilitating the degradation of CIP in the dark. Hence, the degradation of CIP could be realized by utilizing the R-center dot radical triggered through transient photoinitiation with low optical energy consumption.
查看更多>>摘要：In spite of the huge worldwide interest for single-atom and ultradispersed catalysts, metal atoms coordinated with sulfur are rarely addressed. In this work, ultradispersed molybdenum-based catalysts were obtained by adsorption of three thiomolybdates of different nuclearity (n = 1, 2, 3) on high-surface-area S-doped carbon, followed by sulfidation in H2S/H2 flow at 350 degrees C. Scanning transmission electron microscopy (STEM) and X-ray absorption spectroscopy (XAS) attest that single atoms and few-atom clusters are predominant on the surface of the materials after adsorption, as well as after sulfidation and thiophene HDS reaction. Independently on the nature of the thiomolybdate precursor, sulfidation leads to catalysts with specific thiophene HDS activity exceeding that of a conventional supported MoS2 reference. Ultradispersed clusters were further promoted with cobalt, yielding HDS turnover frequencies 2-3 times higher than those of reported benchmark CoMoS catalysts. These findings provide new insights into the previously debated issues of structure-activity relationships for HDS catalysts and expand the range of applications of atomically dispersed catalysts.
查看更多>>摘要：NiFe-based nanostructures have been attracting attentions as a promising non-noble metal electrocatalysts for oxygen evolution reaction in alkaline. In this paper, a bionic sunflower-like NiFe-polydopamine film was prepared via self-polymerization of dopamine-Ni2+/Fe3+ followed by partial pyrolysis process. In the films, NiO quantum dots are embedded in Fe-coupled polydopamine due to the space-confined effect of PDA. The selfactivation process effect led to in-situ reconstruction of the generation of NiOOH and the migration of Fe sites to NiOOH surface. Abundant Fe sites on the NiOOH surface facilitated formation of stable O* intermediate. Moreover, the coordination-confined effect of PDA for Fe ions in the PDA network gave the PDANF catalyst excellent durability. The NiFe-polydopamine film exhibited excellent intrinsic OER activity with a low overpotential of 254.1 mV for 10 mA cm-2 and an unprecedentedly low Tafel slope of 23.3 mV dec-1.
Kim, Chang-HeeFeng, ZhenxingKim, Byung-HyunLee, Seung Woo...
10页
查看更多>>摘要：Ir and its oxide are the only available oxygen evolution reaction (OER) electrocatalysts with reasonably high activity and stability for commercial proton-exchange membrane electrolyzers. However, the establishment of structure-performance relationships for the design of better Ir-based electrocatalysts is hindered by their uncontrolled surface reconstruction during OER in acidic media. Herein, we monitor the structural evolution of two model Ir nanocrystals (one with a flat surface enclosed by (100) facets and the other with a concave surface containing numerous high-index planes) under acidic OER conditions. Operando X-ray absorption spectroscopy measurements reveal that the promotion of surface IrOx formation during the OER by the concave Ir surface with high-index planes results in a gradual OER activity increase, while a decrease in activity and limited oxide formation are observed for the flat Ir surface. After the activation process, the Ir concave surface exhibits similar to 10 times higher activity than the flat surface. Density functional theory computations reveal that Ir high-index surfaces are thermodynamically preferred for the adsorption of oxygen atoms and the formation of surface oxides under OER conditions. Thus, our work establishes a structure-performance relationship for Ir nanocrystals under operating conditions, providing new principles for the design of nanoscale OER electrocatalysts.
查看更多>>摘要：Metal catalyzed dehydration of primary amides is an attractive route for the synthesis of nitriles, but this transformation is often promoted by various environmentally hazardous additives or organic ligands in homogeneous catalysis, which limits its industrial application. The acidic mesoporous ZSM-5 assembled palladium (Pd/ZSM-5-H) was found to be able to systemically convert primary amides to nitriles in the absence of any additives with excellent applicability. The highly dispersive Pd(II) species grafted on ZSM-5-H via the strong binding interaction between AlO4 tetrahedron and Pd species (Pd/ZSM-5-H) drive the significantly higher reaction activity (100%) than Pd/Silicalite-1-H (30%) and Pd(OAc)2 (20%). Furthermore, the active centers of Pd/ ZSM-5-H in the catalytic process were attributed to [PdOH]+ by the acidity characterization and theoretical calculations, and the primary amides to nitriles catalyzed by [PdOH]+ in Pd/ZSM-5-H is thermodynamically and kinetically favorable with -OH group in [PdOH]+ as an agent of proton transfer.
NSTL
Elsevier