The excellent oxygen reduction reaction(ORR)activity of Fe–N–C catalysts in acidic media makes them potential for low-cost proton exchange membrane fuel cells.In recent years,it has been shown that heteroatoms(B,O,S...The excellent oxygen reduction reaction(ORR)activity of Fe–N–C catalysts in acidic media makes them potential for low-cost proton exchange membrane fuel cells.In recent years,it has been shown that heteroatoms(B,O,S,P,Cl,F,etc.)can be used as electron-withdrawing groups to modulate the planar structure and electron distribution of the Fe–Nx active sites to achieve simultaneous improvement of catalytic activity and stability.However,the optimal location of the heteroatoms remains unclear.Here,taking chalcogen heteroatoms(S and Se)as an example,we control the doping positions and investigate their effect on the ORR performance of the Fe–N–C catalysts.The first coordination shell of the iron single atom is identified as the optimal doping position.The optimized catalysts Fe–N_(3)Se_(1)/NC and Fe–N_(3)Se_(1)/NC demonstrate improved activity and stability in both half cells and fuel cells.This work provides insights into the enhancement mechanism of heteroatom doping in single-atom catalysts.展开更多
A series of two-dimensional （2D） conjugated copolymers with spatial D-A-D structures （PTNBTB, PTCBTB, and PTSBTB） consisting of hetero-atom-bridged dithiophene and phenylvinyl-substituted benzothiadiazole blocks i...A series of two-dimensional （2D） conjugated copolymers with spatial D-A-D structures （PTNBTB, PTCBTB, and PTSBTB） consisting of hetero-atom-bridged dithiophene and phenylvinyl-substituted benzothiadiazole blocks in the main chain have been designed, synthesized, and characterized. The structure-property relationships of the resulting copolymers were systematically investigated. The effects of the bridging atoms （N, C, and Si） on their thermal, optical, electrochemical and charge- transporting properties were also studied. PTNBTB exhibits a smaller band gap with red-shifted absorption, whereas PTSBTB possesses deeper HOMO level and higher hole mobility than PTCBTB or PTSBTB. Bulk heterojunction （BHJ） solar cells were fabricated and characterized with the conventional configuration of ITO/PEDOT：PSS/copolymer：PCT^BM （I：I）/Ca/A1. As ex- pected, PTSBTB devices showed the highest PCE, up to 4.01%, which was due to the lower HOMO level, higher carrier mobility, and stronger optical response as well as the finer nanoscale phase separation of the pristine polymer and/or the corresponding blending active layer with PC71BM. The primary results offer useful insights in designing 2D copolymers with spatial D-A-D backbone and different hetero-atom bridged donor units to finely tune the absorptions, electronic energy levels, carrier mobilities and the photovoltaic properties.展开更多
Zeolites Y of FAU type containing different transition metal hetero-atoms(MY or M1M2Y,where M = Ti,Co,Ni,Mo,Zr,etc) in the framework were synthesized.The effect of different hetero-atoms on the crystallinity of zeolit...Zeolites Y of FAU type containing different transition metal hetero-atoms(MY or M1M2Y,where M = Ti,Co,Ni,Mo,Zr,etc) in the framework were synthesized.The effect of different hetero-atoms on the crystallinity of zeolite Y was characterized by XRD and SEM.The zeolites MY or M1M2Y exhibit the same phase profiles as zeolite Y by XRD.SEM results showed that MY zeolite is provided with well-defined crystal and larger crystal size.Zeolite Y containing single transition metal hetero-atom(MY) exhibits lower crystallinity than zeolite Y.However,the zeolite Y containing two suitable hetero-atoms(M1M2Y) has a much higher crystallinity than MY due to the collaboration of M1 and M2;there is an optimum composition for two hetero-atoms to get a high crystallinity.展开更多
基金supported by the National Key Research and Development Program of China(grant No.2021YFB4000601)Natural Science Foundation of Beijing Municipality(grant No.Z200012)+1 种基金National Natural Science Foundation of China(grant No.21975010,U21A20328)the China Postdoctoral Science Foundation(grant No.2022M720013).
文摘The excellent oxygen reduction reaction(ORR)activity of Fe–N–C catalysts in acidic media makes them potential for low-cost proton exchange membrane fuel cells.In recent years,it has been shown that heteroatoms(B,O,S,P,Cl,F,etc.)can be used as electron-withdrawing groups to modulate the planar structure and electron distribution of the Fe–Nx active sites to achieve simultaneous improvement of catalytic activity and stability.However,the optimal location of the heteroatoms remains unclear.Here,taking chalcogen heteroatoms(S and Se)as an example,we control the doping positions and investigate their effect on the ORR performance of the Fe–N–C catalysts.The first coordination shell of the iron single atom is identified as the optimal doping position.The optimized catalysts Fe–N_(3)Se_(1)/NC and Fe–N_(3)Se_(1)/NC demonstrate improved activity and stability in both half cells and fuel cells.This work provides insights into the enhancement mechanism of heteroatom doping in single-atom catalysts.
基金supported by the National Natural Science Foundation of China(20802033,21272164)the National High-Tech R&D Program of China(2013AA031901)+1 种基金the Youth Science and Technology Foundation of Sichuan Province(2013JQ0032)the Fundamental Research Funds for the Central Universities(2012SCU04B01,YJ2011025)
文摘A series of two-dimensional （2D） conjugated copolymers with spatial D-A-D structures （PTNBTB, PTCBTB, and PTSBTB） consisting of hetero-atom-bridged dithiophene and phenylvinyl-substituted benzothiadiazole blocks in the main chain have been designed, synthesized, and characterized. The structure-property relationships of the resulting copolymers were systematically investigated. The effects of the bridging atoms （N, C, and Si） on their thermal, optical, electrochemical and charge- transporting properties were also studied. PTNBTB exhibits a smaller band gap with red-shifted absorption, whereas PTSBTB possesses deeper HOMO level and higher hole mobility than PTCBTB or PTSBTB. Bulk heterojunction （BHJ） solar cells were fabricated and characterized with the conventional configuration of ITO/PEDOT：PSS/copolymer：PCT^BM （I：I）/Ca/A1. As ex- pected, PTSBTB devices showed the highest PCE, up to 4.01%, which was due to the lower HOMO level, higher carrier mobility, and stronger optical response as well as the finer nanoscale phase separation of the pristine polymer and/or the corresponding blending active layer with PC71BM. The primary results offer useful insights in designing 2D copolymers with spatial D-A-D backbone and different hetero-atom bridged donor units to finely tune the absorptions, electronic energy levels, carrier mobilities and the photovoltaic properties.
文摘Zeolites Y of FAU type containing different transition metal hetero-atoms(MY or M1M2Y,where M = Ti,Co,Ni,Mo,Zr,etc) in the framework were synthesized.The effect of different hetero-atoms on the crystallinity of zeolite Y was characterized by XRD and SEM.The zeolites MY or M1M2Y exhibit the same phase profiles as zeolite Y by XRD.SEM results showed that MY zeolite is provided with well-defined crystal and larger crystal size.Zeolite Y containing single transition metal hetero-atom(MY) exhibits lower crystallinity than zeolite Y.However,the zeolite Y containing two suitable hetero-atoms(M1M2Y) has a much higher crystallinity than MY due to the collaboration of M1 and M2;there is an optimum composition for two hetero-atoms to get a high crystallinity.
