Developing an efficient approach of transforming biomass waste to functional carbon-based electrode materials applied in supercapacitor offers an important and high value-added practical application due to the abundan...Developing an efficient approach of transforming biomass waste to functional carbon-based electrode materials applied in supercapacitor offers an important and high value-added practical application due to the abundance and considerable low price of biomass wastes.Herein,a hierarchical carbon functionalized with electrochemical-active oxygen-containing groups was fabricated by microwave treatment from the biomass waste of camellia oleifera.The obtained mesoporous carbon(MAC)owns nanosheet morphology,rich mesoporosity,large surface area(1726 m2/g)and very high oxygenic functionalities(16.2 wt%)with pseudocapacitive activity.Prepared electrode of supercapacitor and tested in 2.0 M H2 SO4,the MAC exhibits an obvious pseudocapacitive activity and achieved a superior supercapacitive performance to that of directly activated carbon(DAC-800)including high specific capacitance(367 F/g vs.298 F/g)and better rate performance(66%vs.44%).The symmetrical supercapacitor based on MAC shows a high capacity of275 F/g,large energy density of 9.55 Wh/kg(at power density of 478 W/kg)and excellent cycling stability with 99%capacitance retention after 10000 continuous charge-discharge,endowing the obtained MAC a promising functional material for electrochemical energy storage.展开更多
ZnGeP_(2)[ZGP] crystals have attracted tremendous attention for their applications as frequency conversion devices.Nevertheless,the existence of native point defects,including at the surface and in the bulk,lowers the...ZnGeP_(2)[ZGP] crystals have attracted tremendous attention for their applications as frequency conversion devices.Nevertheless,the existence of native point defects,including at the surface and in the bulk,lowers their laser-induced damage threshold by increasing their absorption and forming starting points of the damage,limiting their applications.Here,native point defects in a ZGP crystal are fully studied by the combination of high angle annular dark-field scanning transmission electron microscopy[HAADF-STEM] and optical measurements.The atomic structures of the native point defects of the Zn vacancy,P vacancy,and Ge-Zn antisite were directly obtained through an HAADF-STEM,and proved by photoluminescence[PL] spectra at 77 K.The carrier dynamics of these defects are further studied by ultrafast pump-probe spectroscopy,and the decay lifetimes of 180.49,346.73,and 322.82 ps are attributed to the donor V_(p)^(+)→valence band maximum[VBM] recombination,donor Ge^(+)_(Zn)→VBM recombination,and donor–acceptor pair recombination of V_(p)^(+)→V^(-)_(Zn),respectively,which further confirms the assignment of the electron transitions.The diagrams for the energy bands and excited electron dynamics are established based on these ultrahigh spatial and temporal results.Our work is helpful for understanding the interaction mechanism between a ZGP crystal and ultrafast laser,doing good to the ZGP crystal growth and device fabrication.展开更多
In this work, a series of Pt nanocrystallines(Pt NCs) supported on TiO2 substrate with controlled thickness of carbon layers(C-Pt/TiO2) were synthesized. Well-dispersed Pt NCs were facilely synthesized at room tem...In this work, a series of Pt nanocrystallines(Pt NCs) supported on TiO2 substrate with controlled thickness of carbon layers(C-Pt/TiO2) were synthesized. Well-dispersed Pt NCs were facilely synthesized at room temperature by a photo-reduction process in lytropic liquid crystal(LCs). Surface tuning of the carbon layers on Pt/TiO2 catalysts was achieved by varying the calcination atmospheres(in argon, air, and oxygen) and characterized by XPS and HRTEM. The influence of the coated carbon layers on the catalytic activity of catalysts is investigated by CO oxidation reaction which presented the following ranks: C-Pt/TiO2-O2〉 C-Pt/TiO2-Air 〉 C-Pt/TiO2-Ar. It is found that the carbon layer coating can stabilize the Pt NCs and enable them anti-sintering at high temperature. This finding provides new insight into understanding the C-Pt/TiO2 ternary system for tuning their catalytic performance.展开更多
基金financially supported by the National Key Technology R&D Program of China(2017YFB0310704)the National Natural Science Foundation of China(21773112 and 21173119)the Fundamental Research Funds for the Central Universities
文摘Developing an efficient approach of transforming biomass waste to functional carbon-based electrode materials applied in supercapacitor offers an important and high value-added practical application due to the abundance and considerable low price of biomass wastes.Herein,a hierarchical carbon functionalized with electrochemical-active oxygen-containing groups was fabricated by microwave treatment from the biomass waste of camellia oleifera.The obtained mesoporous carbon(MAC)owns nanosheet morphology,rich mesoporosity,large surface area(1726 m2/g)and very high oxygenic functionalities(16.2 wt%)with pseudocapacitive activity.Prepared electrode of supercapacitor and tested in 2.0 M H2 SO4,the MAC exhibits an obvious pseudocapacitive activity and achieved a superior supercapacitive performance to that of directly activated carbon(DAC-800)including high specific capacitance(367 F/g vs.298 F/g)and better rate performance(66%vs.44%).The symmetrical supercapacitor based on MAC shows a high capacity of275 F/g,large energy density of 9.55 Wh/kg(at power density of 478 W/kg)and excellent cycling stability with 99%capacitance retention after 10000 continuous charge-discharge,endowing the obtained MAC a promising functional material for electrochemical energy storage.
基金supported by the National Natural Science Foundation of China(Nos.51872198,52172151,52172002,92163207,51972229,and 51890865)the Natural Science Foundation of Tianjin(No.18JCYBJC42500)+1 种基金the National Defense Science and Technology 173 Program(No.2021-JCJQJJ-0639)the Natural Science Foundation of Heilongjiang Province(No.YQ2020B002)。
文摘ZnGeP_(2)[ZGP] crystals have attracted tremendous attention for their applications as frequency conversion devices.Nevertheless,the existence of native point defects,including at the surface and in the bulk,lowers their laser-induced damage threshold by increasing their absorption and forming starting points of the damage,limiting their applications.Here,native point defects in a ZGP crystal are fully studied by the combination of high angle annular dark-field scanning transmission electron microscopy[HAADF-STEM] and optical measurements.The atomic structures of the native point defects of the Zn vacancy,P vacancy,and Ge-Zn antisite were directly obtained through an HAADF-STEM,and proved by photoluminescence[PL] spectra at 77 K.The carrier dynamics of these defects are further studied by ultrafast pump-probe spectroscopy,and the decay lifetimes of 180.49,346.73,and 322.82 ps are attributed to the donor V_(p)^(+)→valence band maximum[VBM] recombination,donor Ge^(+)_(Zn)→VBM recombination,and donor–acceptor pair recombination of V_(p)^(+)→V^(-)_(Zn),respectively,which further confirms the assignment of the electron transitions.The diagrams for the energy bands and excited electron dynamics are established based on these ultrahigh spatial and temporal results.Our work is helpful for understanding the interaction mechanism between a ZGP crystal and ultrafast laser,doing good to the ZGP crystal growth and device fabrication.
基金financially supported by the National Key Technology R&D Program of China (No. 2017YFB0310704)the National Natural Science Foundation of China (Nos. 21773112, 21173119 and 21303083)+2 种基金Natural Science Foundation of the Higher Education Institutions of Jiangsu Province (No. 17KJB150001)the Natural Science Foundation of Jiangsu Province (No. BK20130563)the Fundamental Research Funds for the Central Universities
文摘In this work, a series of Pt nanocrystallines(Pt NCs) supported on TiO2 substrate with controlled thickness of carbon layers(C-Pt/TiO2) were synthesized. Well-dispersed Pt NCs were facilely synthesized at room temperature by a photo-reduction process in lytropic liquid crystal(LCs). Surface tuning of the carbon layers on Pt/TiO2 catalysts was achieved by varying the calcination atmospheres(in argon, air, and oxygen) and characterized by XPS and HRTEM. The influence of the coated carbon layers on the catalytic activity of catalysts is investigated by CO oxidation reaction which presented the following ranks: C-Pt/TiO2-O2〉 C-Pt/TiO2-Air 〉 C-Pt/TiO2-Ar. It is found that the carbon layer coating can stabilize the Pt NCs and enable them anti-sintering at high temperature. This finding provides new insight into understanding the C-Pt/TiO2 ternary system for tuning their catalytic performance.