查看更多>>摘要：? 2021 Elsevier B.V.Nanosized Cu2O catalysts with precisely controlled bud-to-blooming flower shapes are synthesised using modified polyol method. The evolution of the shape when the catalysts are applied to the gas diffusion electrodes improves the key factors influencing the catalyst layer, e.g. volume porosity and triple-phase boundary contact areas. Numerical and experimental studies revealed increased reactant molar concentration and improved CO2 mass transfer due to the structural changes, which influenced the electrochemical CO2 reduction reaction (eCO2RR). The fully bloomed Cu2O nanoflower catalyst, combined with the two-dimensional (2D) structured graphene sheet, formed a catalyst layer with scaffolding structure that exhibited the highest Faradaic efficiency (FE) of 93.20% towards CO at an applied potential of ?1.0 V vs. RHE in 1 M KOH. These findings established the relationship between the catalyst layer properties and mass transfer, based on which we could describe the effect of the structural design of the catalyst layer on the eCO2RR performance.
查看更多>>摘要：? 2021 Elsevier B.V.Carbon-free electrocatalytic nitrogen reduction reaction (NRR) is an attractive replacement of the current Haber-Bosch method. However, there is a lack of suitable electrocatalysts that simultaneously achieve both high activity and selectivity, hindering the practical applications of NRR. Herein we theoretically design an electron-deficient surface of MoB2 for preferential N2 adsorption and thus increase the local concentration of N2 around the active sites. These lead to outstanding NRR selectivity that can evidently retard the competing HER even at the NRR operating potential. The corresponding theoretical limiting potential for NRR is as low as ? 0.34 V. Our proof-of-concept experiment confirms the above theoretical design, in which excellent NRR performances (NH3 yield rate of ~ 40.94 μg h?1 mg?1, FE of ~ 30.84%) have been achieved. The strategy of inducing electron deficiency on active sites provides new insight into the rational design of NRR electrocatalysts for realizing green and effective ammonia synthesis in practical applications.
查看更多>>摘要：? 2021 Elsevier B.V.The heterogeneous visible-light driven photo-electro-Fenton (H-VL-PEF) system was built to degrade tetracycline using nitrogen/oxygen biomass self-doped porous carbon (NO/PC) cathode catalyst coupling CuFeO2/biochar particle catalyst. The NO/PC possessed the H2O2 selectivity of 85.3%, and the gas diffusion electrode with NO/PC as cathode catalyst (NO/PC-GDE) exhibited fine H2O2 electrogeneration performance and stability. The generated electrons on CuFeO2/biochar by electrostatic induction and light excitation promoted [tbnd]Fe3+/[tbnd]Fe2+ and [tbnd]Cu2+/[tbnd]Cu+ redox cycle, which was beneficial for HO?/O2?- formation and tetracycline degradation. The introduction of CuFeO2/biochar catalyst and visible light could reduce energy consumption and promote tetracycline mineralization. The CuFeO2/biochar loads, initial pH and current density of H-VL-PEF system were optimized. The degradation pathway of tetracycline was speculated based on the intermediates identified by HPLC/MS. Escherichia coli growth inhibition experiments and toxicity prediction analysis demonstrated that the comprehensive toxicity of tetracycline was alleviated due to the catalytic degradation of H-VL-PEF system.
查看更多>>摘要：? 2021 Elsevier B.V.We propose a novel design for smart-catalyst to selective degrade antibiotics and self-report degradation process by combining molecular-imprinting (MI) and afterglow-catalysis. Tetracycline (TC) is used as imprinted template, and ZnGa2O4 doped with Cr3+ (ZGO) is for catalytic degradation even in-the-dark. TC-involved direct hydrothermal-growth of ZGO at 60/80 °C gives MI-ZGO, followed by 750 °C-calcination, and then ethylenediaminetetraacetic-acid (EDTA) etching to get MI-ZGO-750-EDTA. The imprinting mechanism and effect of temperature of MI-ZGO growth on degradation are investigated. The imprinting factor (IF), adsorption/degradation ratio between MI-ZGO-750-EDTA and non-imprinted NI-ZGO-750-EDTA, is used to evaluate the selectivity of three degradation modes (day-and-night, afterglow-catalysis and photo-catalysis). The highest selectivity of 60-MI-ZGO-750-EDTA is gained in afterglow-catalytic degradation, wherein IF of TC is 3 times of oxytetracycline (OTC) and 3.5 times of malachite green (MG) in pure-solutions, while in mixed-solutions, IF of TC is 3.5 times of OTC and 5.2 times of MG. Besides, photoluminescence of MI-ZGO-750-EDTA can self-report degrading process.
查看更多>>摘要：? 2021 Elsevier B.V.Weak light-harvesting capability and low electron-hole separation efficiency remain significant problems unresolved in the design of high-efficient photocatalyst. This work designed and prepared a surface oxygen vacancy (Vo) and graphene quantum dots (GQDs) co-modified Bi2WO6 (GQDs/BWO6?x). It exhibited enhanced photocatalytic conversion of CO2 to CO with a yield of 43.9 μmol·g?1·h?1, which is 1.7-fold higher than Bi2WO6 (BWO). The photogenerated electrons over GQDs/BWO6?x had a longer average fluorescence lifetime (3.3 ns) than BWO (2.7 ns), implying a high electron-hole separation efficiency. The DFT calculation results revealed that the electrons in GQDs/BWO6?x flow from the Vo-remote atoms to the Vo-neighboring atoms instead of confining in the GQDs molecules. Easy transformation of *COOH to *CO, a rate-limiting step, was suggested by an energy barrier calculation result (0.16 eV for GQDs/BWO6?x, 1.12 eV for BWO).
查看更多>>摘要：? 2021 Elsevier B.V.Imine, hydrazone, and olefin-linked covalent organic frameworks (COFs) prosper in visible light photocatalysis. Markedly, the olefin-linked COFs are usually superior in transfer of π-conjugated electron powered by visible light albeit their construction is more challenging. Herein, two olefin-linked COFs were forged between 2,4,6-trimethyl-1,3,5-triazine (TMT) and 2,4,6-tris(4-formyl-phenyl)-1,3,5-triazine (TFPT) or 1,3,5-tris(4-formyl-phenyl)-benzene (TFPB) to afford TTO-COF or TBO-COF, respectively. Both of the olefin-linked COFs based on triazine are of good crystallinity, uniform micropores, and high specific surface areas, but of different morphologies, namely nanotubes and nanosheets. Compared to TBO-COF, TTO-COF nanotubes were constructed with two building blocks based on triazine, which could not only improve the planarity of a single layer but also cause closer stacking of layers in between. Therefore, TTO-COF nanotubes exhibit better photocatalytic performance and stability in the selective oxidation of organic sulfides into corresponding sulfoxides with O2 powered by blue light. Mechanistic investigation evidence the formation of desired sulfoxides was shaped by both electron and energy transfer pathways over TTO-COF nanotubes. This work underlines the ascendancy of olefin-linked COFs inasmuch as they provide an effective platform to construct efficient and durable photocatalysts based on adaptable organic building blocks.
查看更多>>摘要：? 2022How to realize the recycling of homogeneous catalysts has been a great challenge for chemists. In this background, a new pyridinium compound was synthesized and applied in selective photocatalytic oxidation. This photocatalytic system is advantageous in accelerating the transformation of alcohols into acids by two consecutive routes, including (1) photocatalytic oxidation of alcohols to aldehydes; (2) photocatalytic oxidation and autoxidation of aldehydes to acids. By activating molecular oxygen into ?O2? and 1O2, the system displays advantages of high efficiency and simplicity, as well as environment-friendly nature without metals or additives. Attractively, this compound as a homogeneous catalyst can be reused by direct filtration of products profiting from its high performance and stability. The present work develops a new approach to achieve an efficient and recyclable aerobic oxidation of alcohols into acids by using pyridinium-based photocatalysts and provides a valuable insight into the separation and recycling of homogeneous catalysts for economic compatibility and industrial application.
查看更多>>摘要：? 2021 Elsevier B.V.Rational modulation for the composition and structure of the oxygen evolution reaction (OER) electrocatalysts is crucial for overall water splitting. Herein, how to utilize composition change and structure reconstruction via an in situ nonmetal element-doping and leaching-induced strategy to develop robust water oxidation catalysts is firstly proposed. The as-obtained Ni-FeOOH with structural transformation presents a remarkable OER activity with an overpotential of 224 mV at 100 mA/cm2, which is much superior to undoped or unleached catalysts. By tuning the amount of S, the S-doped NiFe-based catalyst exhibits an overpotential of 168 mV at 100 mA/cm2 for the hydrogen evolution reaction. The electrocatalysts with tunable bifunctionality requires only 1.43 V to drive 10 mA/cm2 towards overall water splitting. Systematic experiments and characterizations demonstrate that structural reconstruction into highly active oxyhydroxides species and sufficient activation of lattice oxygen redox reactivity are responsible for the fascinating OER activity induced by S doping/leaching.
查看更多>>摘要：? 2021 Elsevier B.V.Pd@NH2-UiO-66(Zr), with small-sized Pd nanoparticles encapsulated inside the cavities of NH2-UiO-66(Zr), was obtained via a double-solvent impregnation followed by a photoreduction process, which shows superior activity for the visible light initiated syntheses of secondary amines from nitro compounds and alcohols, via a sequential photocatalytic hydrogenation of nitro compounds/dehydrogenation of alcohols, condensation of amines and aldehydes to imines, and the hydrogenation of imines. Simultaneous consumption of photogenerated electrons/holes in the photocatalytic hydrogenation of nitro compounds to amines and dehydrogenation of alcohols to aldehydes promotes the whole reaction. Due to the confinement effect of the cavity and the small-sized Pd nanoparticles, Pd@NH2-UiO-66(Zr) shows significantly superior performance as compared with Pd/NH2-UiO-66(Zr), in which larger Pd nanoparticles are deposited on the surface. This study provides an efficient and green strategy for the production of secondary amines and highlights the great potential of using M/MOFs nanocomposites as multifunctional catalysts for light induced one-pot tandem reactions.
查看更多>>摘要：? 2021 Elsevier B.V.Two atomic layered BiOCl nanosheets with rich oxygen vacancies (NS-OV) were constructed via surface Pd deposition (0.5 wt%) as a multifunctional photocatalyst (Pd0.5/NS-OV), which exhibits high conversion (>95%) and precise selectivity (>98%) for benzylamine coupling to N-benzylidenebenzylamine under visible light irradiation and 1 atm air pressure. XPS and UV–vis DRS indicated that ultrathin structure of the nanosheets induces the formation of surface oxygen vacancies (OV), resulting in abundant surface low-coordinated Bi atoms and expanded visible light absorpion. Moreover, in-situ EPR results revealed that surface OV sites contribute to assemble O2 molecules from air to surface of NS-OV. Additionally, in-situ FTIR suggested that low-coordinated Bi selectively adsorb benzylamine molecules via -N···Bi- coordination bonds at the interfaces, inducing polarization and activation of -C-N bonds. Furthermore, Pd sites were observed to crucially participate in formation of active ?O2- species under visible light irradiation. Based on multifunctional features, a possible synergistic mechanism was proposed.
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