The charge cartier separation and surface catalytic redox reactions are of primary importance as elementary steps in photocatalytic hydrogen evolution. In this study, both of these two processes in photocatalytic hydr...The charge cartier separation and surface catalytic redox reactions are of primary importance as elementary steps in photocatalytic hydrogen evolution. In this study, both of these two processes in photocatalytic hydrogen evolution over graphitic carbon nitride （g-C3N4） were greatly promoted with the earth-abundant ferrites （Co, Ni）Fe2O4 modification. CoFe2O4 was further demonstrated to be a better modifier for g-C3N4 as compared to NiFe2O4, due to the more efficient charge carrier transfer as well as superior surface oxidative catalytic activity. When together loading CoFe2O4 and reductive hydrogen production electrocatalyst Pt onto g-C3N4, the obtained Pt/g-C3N4/CoFe2O4 photocatalyst achieved visible-light （2 〉 420 nm） hydrogen production rate 3.5 times as high as Pt/g-C3N4, with the apparent quantum yield reaching 3.35 % at 420 nm.展开更多
Two-dimensional graphitic carbon nitride（g-C_3N_4） nanosheets（GCNNs） have been considered as an attractive metal-free semiconductor because of their superior catalytic,optical,and electronic properties.However,it ...Two-dimensional graphitic carbon nitride（g-C_3N_4） nanosheets（GCNNs） have been considered as an attractive metal-free semiconductor because of their superior catalytic,optical,and electronic properties.However,it is still challenging to prepare monolayer GCNNs with a reduced lateral size in nanoscale.Herein,a highly efficient ultrasonic technique was used to prepare nanosized monolayer graphitic carbon nitride nanosheets（NMGCNs） with a thickness of around 0.6 nm and an average lateral size of about 55 nm.With a reduced lateral size yet monolayer thickness,NMGCNs show unique photo-responsive properties as compared to both large-sized GCNNs and GCN quantum dots.A dispersion of NMGCNs in water has good stability and exhibits strong blue fluorescence with a high quantum yield of 32%,showing good biocompatibility for cell imaging.Besides,compared to the multilayer GCNNs,NMGCNs show a highly improved photocatalysis under visible light irradiation.Overall,NMGCNs,characterized with monolayer and nanosized lateral dimension,fill the gap between large size（very high aspect ratio） and quantum dot-like counterparts,and show great potential applications as sensors,photo-related and electronic devices.展开更多
The atomistic mechanism for direct conversion of graphite to diamond is a long-standing problem in condensed matter physics. The newly identified cold-compressed graphite phases of M, W and 0 carbon provide a crucial ...The atomistic mechanism for direct conversion of graphite to diamond is a long-standing problem in condensed matter physics. The newly identified cold-compressed graphite phases of M, W and 0 carbon provide a crucial link to understand the graphite-to- diamond phase transformation. We demonstrate by ab initio calculations that pressure has a dual role in lowering the conversion barrier and enhancing the production stability during the first-stage cold-compressed phase conversion of graphite toward the intermediate metastable M, W and 0 carbon phases. However, it has little effect on the relative enthalpy and high conversion barrier during the second-stage conversion process toward the diamond polytypes, showing a temperature dominated conversion process. These results may give explanation regarding the necessity of high pressure and high temperature during the graphite-to- diamond reaction.展开更多
基金the National Natural Science Foundation of China (51323011 and 51236007)the Program for New Century Excellent Talents in University (NCET-130455)+4 种基金the Natural Science Foundation of Shaanxi Province (2014KW07-02)the Natural Science Foundation of Jiangsu Province (BK20141212)the Nano Research Program of Suzhou City (ZXG201442 and ZXG2013003)the Foundation for the Author of National Excellent Doctoral Dissertation of China (201335)the Fundamental Research Funds for the Central Universities
文摘The charge cartier separation and surface catalytic redox reactions are of primary importance as elementary steps in photocatalytic hydrogen evolution. In this study, both of these two processes in photocatalytic hydrogen evolution over graphitic carbon nitride （g-C3N4） were greatly promoted with the earth-abundant ferrites （Co, Ni）Fe2O4 modification. CoFe2O4 was further demonstrated to be a better modifier for g-C3N4 as compared to NiFe2O4, due to the more efficient charge carrier transfer as well as superior surface oxidative catalytic activity. When together loading CoFe2O4 and reductive hydrogen production electrocatalyst Pt onto g-C3N4, the obtained Pt/g-C3N4/CoFe2O4 photocatalyst achieved visible-light （2 〉 420 nm） hydrogen production rate 3.5 times as high as Pt/g-C3N4, with the apparent quantum yield reaching 3.35 % at 420 nm.
基金supported by the National Basic Research Program of China(2014CB932400)the National Natural Science Foundation of China(51525204 and 51302274)+1 种基金Shenzhen Basic Research Project(ZDSYS20140509172959981)the Key Laboratory of Advanced Materials of Ministry of Education(2016AML02)
文摘Two-dimensional graphitic carbon nitride（g-C_3N_4） nanosheets（GCNNs） have been considered as an attractive metal-free semiconductor because of their superior catalytic,optical,and electronic properties.However,it is still challenging to prepare monolayer GCNNs with a reduced lateral size in nanoscale.Herein,a highly efficient ultrasonic technique was used to prepare nanosized monolayer graphitic carbon nitride nanosheets（NMGCNs） with a thickness of around 0.6 nm and an average lateral size of about 55 nm.With a reduced lateral size yet monolayer thickness,NMGCNs show unique photo-responsive properties as compared to both large-sized GCNNs and GCN quantum dots.A dispersion of NMGCNs in water has good stability and exhibits strong blue fluorescence with a high quantum yield of 32%,showing good biocompatibility for cell imaging.Besides,compared to the multilayer GCNNs,NMGCNs show a highly improved photocatalysis under visible light irradiation.Overall,NMGCNs,characterized with monolayer and nanosized lateral dimension,fill the gap between large size（very high aspect ratio） and quantum dot-like counterparts,and show great potential applications as sensors,photo-related and electronic devices.
基金supported by the National Natural Science Foundation of China(Grant No.11274356)the Ministry of Environmental Protection of China(Grant Nos.200909086 and 201109037)
文摘The atomistic mechanism for direct conversion of graphite to diamond is a long-standing problem in condensed matter physics. The newly identified cold-compressed graphite phases of M, W and 0 carbon provide a crucial link to understand the graphite-to- diamond phase transformation. We demonstrate by ab initio calculations that pressure has a dual role in lowering the conversion barrier and enhancing the production stability during the first-stage cold-compressed phase conversion of graphite toward the intermediate metastable M, W and 0 carbon phases. However, it has little effect on the relative enthalpy and high conversion barrier during the second-stage conversion process toward the diamond polytypes, showing a temperature dominated conversion process. These results may give explanation regarding the necessity of high pressure and high temperature during the graphite-to- diamond reaction.
