Atomic clusters typically exhibit distinctive electronic structures and physicochemical properties.However,as the size decreases,their ability to adsorb and dissociate water also diminishes,thereby affecting chemical ...Atomic clusters typically exhibit distinctive electronic structures and physicochemical properties.However,as the size decreases,their ability to adsorb and dissociate water also diminishes,thereby affecting chemical reactions involving water molecules.Enhancing the adsorption and dissociation capabilities of atomic clusters towards water molecules and elucidating the mechanisms underlying their performance enhancement have become important research directions.Herein,employing the carrier-anchored strategy,Ru-O-Ru atomic clusters were prepared and displayed excellent activity and durability in the hydrogen evolution reaction.Specifically,the Ru-O-Ru atomic clusters exhibited only 86 mV overpotential at 100 mA·cm−^(2) and superior membrane-electrode-assembly activity than commercial Ru/C catalyst.Synchrotron radiation-based Fourier transform infrared spectroscopic measurements revealed that the modification of oxygen in Ru-O-Ru units promoted the reorientation of water molecules from a H-up orientation to H-down,therefore,enhanced the formation of strong hydrogen-bond network of interfacial water on the surface of Ru-O-Ru clusters,leading to enhanced adsorption and dissociation of water and accelerated Volmer step.Those findings provide a potential strategy and deep insights for the development of atomic clusters in electrocatalysts.展开更多
Iron-based catalysts have been explored for selective catalytic reduction(SCR)of NO due to environmentally benign characters and good SCR activity.Mn-W-Sb modified siderite catalysts were prepared by impregnation meth...Iron-based catalysts have been explored for selective catalytic reduction(SCR)of NO due to environmentally benign characters and good SCR activity.Mn-W-Sb modified siderite catalysts were prepared by impregnation method based on siderite ore,and SCR perfor-mance of the catalysts was investigated.The catalysts were analyzed by X-ray diffrac-tion,H_(2)-temperature-programmed reduction,Brunauer-Emmett-Teller,Thermogravimetry-derivative thermogravimetry and in-situ diffused reflectance infrared Fourier transform spectroscopy(DRIFTS).The modified siderite catalysts calcined at 450℃ mainly consist of Fe_(2)O_(3),and added Mn,W and Sb species are amorphous.3Mn-5W-1.5Sb-siderite catalyst has a wide temperature window of 180-360℃ and good N_(2) selectivity at low temperatures.In-situ DRIFTS results show NH_(4)^(+),coordinated NH_(3),NH_(2),NO_(3)^(-)species(bidentate),NO_(2)-species(nitro,nitro-nitrito,monodentate),and adsorbed NO_(2) can be discovered on the sur-face of Mn-W-Sb modified siderite catalysts,and doping of Mn will enhance adsorbed NO_(2) formation by synergistic catalysis with Fe^(3+).In addition,the addition of Sb can inhibit sulfates formation on the surface of the catalyst in the presence of SO_(2) and H_(2)O.Time-dependent in-situ DRIFTS studies also indicate that both of Lewis and Br?nsted acid sites play a role in SCR of NO by ammonia at low temperatures.The mechanism of NO removal on the 3Mn-5W-1.5Sb-siderite catalyst can be discovered as a combination of Eley-Rideal and Langmuir-Hinshelwood mechanisms with three reaction pathways.The mechanism of NO,oxidized by synergistic catalysis of Fe^(3+)and Mn^(4+/3+)to form NO_(2) among three pathways,reveals the reason of high NO_(x) conversion of the catalyst at medium and low temperatures.展开更多
A series of Pd/Co_3O_4 catalysts were prepared by Self-Propagating High-Temperature Synthesis(SHS)method in this study, and electric field was applied for catalytic combustion of lean methane over Pd/Co_3O_4 catalysts...A series of Pd/Co_3O_4 catalysts were prepared by Self-Propagating High-Temperature Synthesis(SHS)method in this study, and electric field was applied for catalytic combustion of lean methane over Pd/Co_3O_4 catalysts at low temperature. When electric field was applied, the catalytic combustion performance of Pd/Co_3O_4 catalysts was greatly improved, and the application of electric field could reduce the load of active element Pd to some extent while maintaining the same efficiency. Based on experimental tests and the analysis results of X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), H2-temperature-programmed reduction(H2-TPR) and in-situ diffuse reflectance infrared Fourier transform spectroscopy(in-situ DRIFTS), the mechanism of catalytic oxidation of CH_4 over Pd/Co_3O_4 catalysts in electric field was proposed. The catalytic combustion of CH_4 occurs only when the temperature is higher than 250?C normally, but when electric field was applied, the whole process of CH_4 oxidation was promoted significantly and the reaction temperature was reduced. Electric field could promote the reduction of the support Co_3O_4 to release the lattice oxygen, resulting in the increase of PdOxand the surface chemisorbed oxygen, which could provide more active sites for the low-temperature oxidation of CH_4. Furthermore, electric field could accelerate the dehydroxylation of CoOOH to further enhance the activity of the catalysts.展开更多
基金supported by the National Natural Science Foundation of China(Nos.12025505,22179125,and 12205304)the National Key R&D Program of China(No.2021YFA1600800)+4 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB0450200)the University of China Innovation Program of Anhui Province(No.GXXT-2020-053)the Youth Innovation Promotion Association CAS(No.2022458)the Fundamental Research Funds for the Central Universities(Nos.WK2060000038 and WK2310000113)the Fellowship of China Postdoctoral Science Foundation(No.2021TQ0319).
文摘Atomic clusters typically exhibit distinctive electronic structures and physicochemical properties.However,as the size decreases,their ability to adsorb and dissociate water also diminishes,thereby affecting chemical reactions involving water molecules.Enhancing the adsorption and dissociation capabilities of atomic clusters towards water molecules and elucidating the mechanisms underlying their performance enhancement have become important research directions.Herein,employing the carrier-anchored strategy,Ru-O-Ru atomic clusters were prepared and displayed excellent activity and durability in the hydrogen evolution reaction.Specifically,the Ru-O-Ru atomic clusters exhibited only 86 mV overpotential at 100 mA·cm−^(2) and superior membrane-electrode-assembly activity than commercial Ru/C catalyst.Synchrotron radiation-based Fourier transform infrared spectroscopic measurements revealed that the modification of oxygen in Ru-O-Ru units promoted the reorientation of water molecules from a H-up orientation to H-down,therefore,enhanced the formation of strong hydrogen-bond network of interfacial water on the surface of Ru-O-Ru clusters,leading to enhanced adsorption and dissociation of water and accelerated Volmer step.Those findings provide a potential strategy and deep insights for the development of atomic clusters in electrocatalysts.
基金This work was supported by the National Natural Science Foundation of China(Nos.51406077 and 51276039).
文摘Iron-based catalysts have been explored for selective catalytic reduction(SCR)of NO due to environmentally benign characters and good SCR activity.Mn-W-Sb modified siderite catalysts were prepared by impregnation method based on siderite ore,and SCR perfor-mance of the catalysts was investigated.The catalysts were analyzed by X-ray diffrac-tion,H_(2)-temperature-programmed reduction,Brunauer-Emmett-Teller,Thermogravimetry-derivative thermogravimetry and in-situ diffused reflectance infrared Fourier transform spectroscopy(DRIFTS).The modified siderite catalysts calcined at 450℃ mainly consist of Fe_(2)O_(3),and added Mn,W and Sb species are amorphous.3Mn-5W-1.5Sb-siderite catalyst has a wide temperature window of 180-360℃ and good N_(2) selectivity at low temperatures.In-situ DRIFTS results show NH_(4)^(+),coordinated NH_(3),NH_(2),NO_(3)^(-)species(bidentate),NO_(2)-species(nitro,nitro-nitrito,monodentate),and adsorbed NO_(2) can be discovered on the sur-face of Mn-W-Sb modified siderite catalysts,and doping of Mn will enhance adsorbed NO_(2) formation by synergistic catalysis with Fe^(3+).In addition,the addition of Sb can inhibit sulfates formation on the surface of the catalyst in the presence of SO_(2) and H_(2)O.Time-dependent in-situ DRIFTS studies also indicate that both of Lewis and Br?nsted acid sites play a role in SCR of NO by ammonia at low temperatures.The mechanism of NO removal on the 3Mn-5W-1.5Sb-siderite catalyst can be discovered as a combination of Eley-Rideal and Langmuir-Hinshelwood mechanisms with three reaction pathways.The mechanism of NO,oxidized by synergistic catalysis of Fe^(3+)and Mn^(4+/3+)to form NO_(2) among three pathways,reveals the reason of high NO_(x) conversion of the catalyst at medium and low temperatures.
基金the National Key R&D Program of China(No.2016YFC0208000)the National Natural Science Foundation of China(No.51676127)
文摘A series of Pd/Co_3O_4 catalysts were prepared by Self-Propagating High-Temperature Synthesis(SHS)method in this study, and electric field was applied for catalytic combustion of lean methane over Pd/Co_3O_4 catalysts at low temperature. When electric field was applied, the catalytic combustion performance of Pd/Co_3O_4 catalysts was greatly improved, and the application of electric field could reduce the load of active element Pd to some extent while maintaining the same efficiency. Based on experimental tests and the analysis results of X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), H2-temperature-programmed reduction(H2-TPR) and in-situ diffuse reflectance infrared Fourier transform spectroscopy(in-situ DRIFTS), the mechanism of catalytic oxidation of CH_4 over Pd/Co_3O_4 catalysts in electric field was proposed. The catalytic combustion of CH_4 occurs only when the temperature is higher than 250?C normally, but when electric field was applied, the whole process of CH_4 oxidation was promoted significantly and the reaction temperature was reduced. Electric field could promote the reduction of the support Co_3O_4 to release the lattice oxygen, resulting in the increase of PdOxand the surface chemisorbed oxygen, which could provide more active sites for the low-temperature oxidation of CH_4. Furthermore, electric field could accelerate the dehydroxylation of CoOOH to further enhance the activity of the catalysts.
