As a powerful and sensitive tool for the characterization of zeolite building units,UV Raman spectroscopy has been used to monitor interzeolite transformation from FAU to CHA and MFI zeolites.The results show that the...As a powerful and sensitive tool for the characterization of zeolite building units,UV Raman spectroscopy has been used to monitor interzeolite transformation from FAU to CHA and MFI zeolites.The results show that the behavior of double 6-membered rings(D6Rs)in the FAU zeolite framework plays an important role during the formation of the target product in the interzeolite transformation.For the transformation of FAU to CHA,because both zeolites contain the same D6R units,direct transformation occurs,in which the D6Rs were largely unchanged.In contrast,for the transformation of FAU to MFI,the D6Rs can be divided into two single 6-membered rings(S6Rs),which further assembled into the MFI structure.In this crystallization,5-membered rings(5Rs)are only observed in the MFI framework formation,suggesting that the basic building units in the transformation of FAU to MFI are S6Rs rather than 5Rs.These insights will be helpful for further understanding of the interzeolite transformation.展开更多
Tailoring the Ti coordination states in titanosilicate zeolites to simultaneously improve feedstock conversion and maximize the target product selectivity remains a challenge in the pursuit of high-performance catalys...Tailoring the Ti coordination states in titanosilicate zeolites to simultaneously improve feedstock conversion and maximize the target product selectivity remains a challenge in the pursuit of high-performance catalysts for selective oxidation reactions.Herein,we provide a facile strategy to synthesize hierarchical anatase-free TS-1(MFI-type)zeolites with tetrahedrally coordinated(TiO_(4))and octahedrally coordinated Ti species(TiO_(6)).The TiO_(4)species provide high epoxide selectivity,while the TiO_(6)species afford improved alkene conversion.This strategy is achieved by synergistically using an L-lysine-assisted approach and a two-step crystallization;the two-step crystallization approach prevents the formation of anatase TiO_(2),while L-lysine stabilizes the TiO_(6)species and ensures efficient incorporation of TiO_(6)into the anatase-free TS-1 zeolites.Compared with their conventional counterparts,which only contain TiO_(4)species,the as-prepared TS-1 zeolites(Si/Ti=36.9)result in a higher 1-hexene conversion(33%),higher TON value(153),and comparable epoxide selectivity(95%).This synthetic strategy provides avenues to tailor the amount and distribution of Ti species in titanosilicate zeolites to achieve high catalytic performances in various processes.展开更多
Investigation of the charge dynamics and roles of cocatalysts is crucial for understanding the reaction of photocatalytic water splitting on semiconductor photocatalysts.In this work,the dynamics of photogenerated ele...Investigation of the charge dynamics and roles of cocatalysts is crucial for understanding the reaction of photocatalytic water splitting on semiconductor photocatalysts.In this work,the dynamics of photogenerated electrons in Ga_(2)O_(3) loaded with Cr_(2)O_(3)-Rh cocatalysts was studied using time-resolved mid-infrared spectroscopy.The structure of these Cr_(2)O_(3)-Rh cocatalysts was identified with high-resolution transmission electron microscopy and CO adsorption Fourier-transform infrared spectroscopy,as Rh particles partly covered with Cr_(2)O_(3).The decay dynamics of photogenerated electrons reveals that only the electrons trapped by the Rh particles efficiently participate in the H2 evolution reaction.The loaded Cr_(2)O_(3) promotes electron transfer from Ga_(2)O_(3) to Rh,which accelerates the electron-consuming reaction for H2 evolution.Based on these observations,a photocatalytic water-splitting mechanism for Cr_(2)O_(3)-Rh/Ga_(2)O_(3) photocatalysts has been proposed.The elucidation of the roles of the Cr_(2)O_(3)-Rh cocatalysts aids in further understanding the reaction mechanisms of photocatalytic water splitting and guiding the development of improved photocatalysts.展开更多
Although photocatalytic water splitting has excellent potential for converting solar energy into chemical energy,the challenging charge separation process and sluggish surface catalytic reactions significantly limit p...Although photocatalytic water splitting has excellent potential for converting solar energy into chemical energy,the challenging charge separation process and sluggish surface catalytic reactions significantly limit progress in solar energy conversion using semiconductor photocatalysts.Herein,we demonstrate a feasible strategy involving the surface assembly of cobalt oxide species(CoO_(x))on a visible-light-responsive Cd_(0.9)Zn_(0.1)S(CZS)photocatalyst to fabricate a hierarchical CZS@CoO_(x) heterostructure.The unique hierarchical structure effectively accelerates the directional transfer of photogenerated charges,reducing charge recombination through the smooth interfacial heterojunction between CZS and CoO_(x),as evidenced by photoluminescence(PL)spectroscopy and various electrochemical characterizations.The surface cobalt species on the CZS material also act as efficient cocatalysts for photocatalytic hydrogen production,with activity even higher than that of noble metals.The well-defined CZS@CoO_(x) heterostructure not only enhances the interfacial separation of photoinduced charges,but also improves surface catalytic reactions.This leads to superior photocatalytic performances,with an apparent quantum efficiency of 20%at 420 nm for visible-light-driven hydrogen generation,which is one of the highest quantum efficiencies measured among noble-metal-free photocatalysts.Our work presents a potential pathway for controlling complex charge separation and catalytic reaction processes in photocatalysis,guiding the practical development of artificial photocatalysts for successful transformation of solar to chemical energy.展开更多
Development of the sustainable routes for synthesis of ITQ-family zeolites is very important because of their unique structures and excellent catalytic and adsorptive properties.The burden of costly raw materials and ...Development of the sustainable routes for synthesis of ITQ-family zeolites is very important because of their unique structures and excellent catalytic and adsorptive properties.The burden of costly raw materials and low efficiency of synthesis put a strong challenge for their widespread commercial application.Here,we show an alternative and simple route for synthesis of ITQ-12,ITQ-13,and ITQ-17 zeolites using commercially available organic templates by a facile grinding process of anhydrous starting raw solids,followed by heating at 140-180 ℃.Compared with the conventional hydrothermal synthesis,this approach has obvious advantages such as employment of low-cost organic templates with very high effectiveness,high yield of zeolite products,short crystallization time,and relatively simple procedures.This methodology might open a pathway to synthesize ITQ zeolites with more sustainable manner.展开更多
The development of visible-light-responsive photocatalysts for promoting solar-driven oxygen(O2)production from water splitting is a potentially attractive but still a challenging scheme.In the present work,a(111)-typ...The development of visible-light-responsive photocatalysts for promoting solar-driven oxygen(O2)production from water splitting is a potentially attractive but still a challenging scheme.In the present work,a(111)-type layered perovskite oxynitride,Sr5Nb4O15-xNx,was synthesized via the nitridation treatment of the disk-like oxide precursor under the ammonia flow,which was fabricated using a flux method.The homogeneous dispersion of nitrogen(N)dopant in N-doped Sr5Nb4O15 was ascertained by energy-dispersive X-ray spectroscopy characterization,and the Sr5Nb4O15-xNx was found to be a direct semiconductor with a light absorption edge of approximately 640 nm.Density functional theory investigation implies that the hybridization between the outmost N 2p orbitals and O 2p orbitals upshifts the original valence band maximum of Sr5Nb4O15 and endows its visible-light-responsive characteristics.Loading with cobalt oxide(CoOx)as cocatalyst,the as-prepared Sr5Nb4O15-xNx exhibited an enhanced photocatalytic O2 evolution activity from water splitting under visible-light illumination(λ>420 nm).Moreover,another homogeneous N-doped layered perovskite-type niobium(Nb)-based oxynitride,Ba5Nb4O15-xNx,was also developed and investigated for the visible-light-actuated O2 production,highlighting the versatility of the present approach for exploring novel visible-light-responsive photocatalysts.展开更多
基金supported by the National Key R&D Program of China(2017YFB0702800)the National Natural Science Foundation of China(2152780065,91634201 and 21720102001)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB17000000)~~
文摘As a powerful and sensitive tool for the characterization of zeolite building units,UV Raman spectroscopy has been used to monitor interzeolite transformation from FAU to CHA and MFI zeolites.The results show that the behavior of double 6-membered rings(D6Rs)in the FAU zeolite framework plays an important role during the formation of the target product in the interzeolite transformation.For the transformation of FAU to CHA,because both zeolites contain the same D6R units,direct transformation occurs,in which the D6Rs were largely unchanged.In contrast,for the transformation of FAU to MFI,the D6Rs can be divided into two single 6-membered rings(S6Rs),which further assembled into the MFI structure.In this crystallization,5-membered rings(5Rs)are only observed in the MFI framework formation,suggesting that the basic building units in the transformation of FAU to MFI are S6Rs rather than 5Rs.These insights will be helpful for further understanding of the interzeolite transformation.
文摘Tailoring the Ti coordination states in titanosilicate zeolites to simultaneously improve feedstock conversion and maximize the target product selectivity remains a challenge in the pursuit of high-performance catalysts for selective oxidation reactions.Herein,we provide a facile strategy to synthesize hierarchical anatase-free TS-1(MFI-type)zeolites with tetrahedrally coordinated(TiO_(4))and octahedrally coordinated Ti species(TiO_(6)).The TiO_(4)species provide high epoxide selectivity,while the TiO_(6)species afford improved alkene conversion.This strategy is achieved by synergistically using an L-lysine-assisted approach and a two-step crystallization;the two-step crystallization approach prevents the formation of anatase TiO_(2),while L-lysine stabilizes the TiO_(6)species and ensures efficient incorporation of TiO_(6)into the anatase-free TS-1 zeolites.Compared with their conventional counterparts,which only contain TiO_(4)species,the as-prepared TS-1 zeolites(Si/Ti=36.9)result in a higher 1-hexene conversion(33%),higher TON value(153),and comparable epoxide selectivity(95%).This synthetic strategy provides avenues to tailor the amount and distribution of Ti species in titanosilicate zeolites to achieve high catalytic performances in various processes.
文摘Investigation of the charge dynamics and roles of cocatalysts is crucial for understanding the reaction of photocatalytic water splitting on semiconductor photocatalysts.In this work,the dynamics of photogenerated electrons in Ga_(2)O_(3) loaded with Cr_(2)O_(3)-Rh cocatalysts was studied using time-resolved mid-infrared spectroscopy.The structure of these Cr_(2)O_(3)-Rh cocatalysts was identified with high-resolution transmission electron microscopy and CO adsorption Fourier-transform infrared spectroscopy,as Rh particles partly covered with Cr_(2)O_(3).The decay dynamics of photogenerated electrons reveals that only the electrons trapped by the Rh particles efficiently participate in the H2 evolution reaction.The loaded Cr_(2)O_(3) promotes electron transfer from Ga_(2)O_(3) to Rh,which accelerates the electron-consuming reaction for H2 evolution.Based on these observations,a photocatalytic water-splitting mechanism for Cr_(2)O_(3)-Rh/Ga_(2)O_(3) photocatalysts has been proposed.The elucidation of the roles of the Cr_(2)O_(3)-Rh cocatalysts aids in further understanding the reaction mechanisms of photocatalytic water splitting and guiding the development of improved photocatalysts.
文摘Although photocatalytic water splitting has excellent potential for converting solar energy into chemical energy,the challenging charge separation process and sluggish surface catalytic reactions significantly limit progress in solar energy conversion using semiconductor photocatalysts.Herein,we demonstrate a feasible strategy involving the surface assembly of cobalt oxide species(CoO_(x))on a visible-light-responsive Cd_(0.9)Zn_(0.1)S(CZS)photocatalyst to fabricate a hierarchical CZS@CoO_(x) heterostructure.The unique hierarchical structure effectively accelerates the directional transfer of photogenerated charges,reducing charge recombination through the smooth interfacial heterojunction between CZS and CoO_(x),as evidenced by photoluminescence(PL)spectroscopy and various electrochemical characterizations.The surface cobalt species on the CZS material also act as efficient cocatalysts for photocatalytic hydrogen production,with activity even higher than that of noble metals.The well-defined CZS@CoO_(x) heterostructure not only enhances the interfacial separation of photoinduced charges,but also improves surface catalytic reactions.This leads to superior photocatalytic performances,with an apparent quantum efficiency of 20%at 420 nm for visible-light-driven hydrogen generation,which is one of the highest quantum efficiencies measured among noble-metal-free photocatalysts.Our work presents a potential pathway for controlling complex charge separation and catalytic reaction processes in photocatalysis,guiding the practical development of artificial photocatalysts for successful transformation of solar to chemical energy.
文摘Development of the sustainable routes for synthesis of ITQ-family zeolites is very important because of their unique structures and excellent catalytic and adsorptive properties.The burden of costly raw materials and low efficiency of synthesis put a strong challenge for their widespread commercial application.Here,we show an alternative and simple route for synthesis of ITQ-12,ITQ-13,and ITQ-17 zeolites using commercially available organic templates by a facile grinding process of anhydrous starting raw solids,followed by heating at 140-180 ℃.Compared with the conventional hydrothermal synthesis,this approach has obvious advantages such as employment of low-cost organic templates with very high effectiveness,high yield of zeolite products,short crystallization time,and relatively simple procedures.This methodology might open a pathway to synthesize ITQ zeolites with more sustainable manner.
基金the financial support from the National Key R&D Program of China(No.2020YFA0406102)the National Natural Science Foundation of China(Nos.21633009 and 21925206)+2 种基金the International Partnership Program of Chinese Academy of Sciences(No.121421KYSB20190025)the Dalian National Laboratory for Clean Energy(DNL)Cooperation Fund,CAS(No.DNL 201913)the DICP Foundation of Innovative Research(No.DICP I201927)。
文摘The development of visible-light-responsive photocatalysts for promoting solar-driven oxygen(O2)production from water splitting is a potentially attractive but still a challenging scheme.In the present work,a(111)-type layered perovskite oxynitride,Sr5Nb4O15-xNx,was synthesized via the nitridation treatment of the disk-like oxide precursor under the ammonia flow,which was fabricated using a flux method.The homogeneous dispersion of nitrogen(N)dopant in N-doped Sr5Nb4O15 was ascertained by energy-dispersive X-ray spectroscopy characterization,and the Sr5Nb4O15-xNx was found to be a direct semiconductor with a light absorption edge of approximately 640 nm.Density functional theory investigation implies that the hybridization between the outmost N 2p orbitals and O 2p orbitals upshifts the original valence band maximum of Sr5Nb4O15 and endows its visible-light-responsive characteristics.Loading with cobalt oxide(CoOx)as cocatalyst,the as-prepared Sr5Nb4O15-xNx exhibited an enhanced photocatalytic O2 evolution activity from water splitting under visible-light illumination(λ>420 nm).Moreover,another homogeneous N-doped layered perovskite-type niobium(Nb)-based oxynitride,Ba5Nb4O15-xNx,was also developed and investigated for the visible-light-actuated O2 production,highlighting the versatility of the present approach for exploring novel visible-light-responsive photocatalysts.
