The exfoliation of bulk graphitic carbon nitride(g-C_(3)N_(4))into monolayer has been intensively studied to induce maximum sur-face area for fundamental studies,but ended in failure to realize chemi-cally and physica...The exfoliation of bulk graphitic carbon nitride(g-C_(3)N_(4))into monolayer has been intensively studied to induce maximum sur-face area for fundamental studies,but ended in failure to realize chemi-cally and physically well-defined monolayer of g-C_(3)N_(4)mostly due to the difficulty in reducing the layer thickness down to an atomic level.It has,therefore,remained as a challenging issue in two-dimensional(2D)chemistry and physics communities.In this study,an“atomic monolayer of g-C_(3)N_(4)with perfect two-dimensional limit”was successfully prepared by the chemically well-defined two-step routes.The atomically resolved monolayer of g-C_(3)N_(4)was also confirmed by spectroscopic and micro-scopic analyses.In addition,the experimental Cs-HRTEM image was collected,for the first time,which was in excellent agreement with the theoretically simulated;the evidence of monolayer of g-C_(3)N_(4)in the perfect 2D limit becomes now clear from the HRTEM image of orderly hexagonal symmetry with a cavity formed by encirclement of three adjacent heptazine units.Compared to bulk g-C_(3)N_(4),the present g-C_(3)N_(4)monolayer showed significantly higher photocatalytic gen-eration of H2O2 and H2,and electrocatalytic oxygen reduction reaction.In addition,its photocatalytic efficiency for H2O2 production was found to be the best for any known g-C_(3)N_(4)nanomaterials,underscoring the remarkable advantage of monolayer formation in optimizing the catalyst performance of g-C_(3)N_(4).展开更多
Pd-MoO3/SiO2 catalyst has been prepared using the method of incipient wetness impregnation. The photo absorbing behaviors and chemisorbing properties of the catalyst have been characterized by UV-vis spectra and TPD-M...Pd-MoO3/SiO2 catalyst has been prepared using the method of incipient wetness impregnation. The photo absorbing behaviors and chemisorbing properties of the catalyst have been characterized by UV-vis spectra and TPD-MS experiments. The results indicated that metal Pd loaded on MoOa/SiO2 has a significant effect on the photo absorbing performance of MoOa/SiO2, and an obvious blue shift of the absorption edge is produced. Under UV irradiation, the chemisorption state of CO2 undergoes decomposing process to form CO at 481 K, and a two-site adsorption state of ethane can be formed at around 496 K. Photo-oxidation of ethane using carbon dioxide can mainly produce propanal, ethanol and acetaldehyde in the temperature range of 353-423 K. The presence of metal Pd improves the catalytic activity remarkably.展开更多
Graphitic carbon nitride(g-C_(3)N_(4)) is a fascinating photocatalyst for solar energy utilization in photo-catalysis.Nevertheless,it often suffers from moderate photo-catalytic activity due to its low specific surfac...Graphitic carbon nitride(g-C_(3)N_(4)) is a fascinating photocatalyst for solar energy utilization in photo-catalysis.Nevertheless,it often suffers from moderate photo-catalytic activity due to its low specific surface area and fast recombination rate of photogenerated electrons upon photo-excitation.Herein,we overcome the bottlenecks by constructing a porous g-C_(3)N_(4) nanosheet(PCNS)through a simple thermal oxidation etching method.Benefited from its porous layer structure,the obtained PCNS exhibits large specific surface area,efficient separation of photogenerated charge carriers,as well as high exposure of active sites.As a result,it is robust and universal in visible light-driven dehydrogenation of alcohols in water under oxidant-free condition.Almost quantitative yields(>99%)of various valuable carbonyl compounds were obtained over PCNS,while bulk g-C_(3)N_(4) was far less efficient.Moreover,the photo-catalyst was highly stable and could be facilely recovered from the aqueous system for efficient reuse.The easy preparation and excellent performance made PCNS a promising and competitive photocatalyst for the solar applications.展开更多
A novel visible light active photo-catalyst named CHC/C-PVA/TiO2, the composite of titanium dioxide（TiO2）with conjugated derivative of polyvinyl alcohol（C-PVA） loaded on a cordierite honeycomb ceramic（CHC）substr...A novel visible light active photo-catalyst named CHC/C-PVA/TiO2, the composite of titanium dioxide（TiO2）with conjugated derivative of polyvinyl alcohol（C-PVA） loaded on a cordierite honeycomb ceramic（CHC）substrate, was fabricated by combining the synthesis of TiO2 sol, preparation of C-PVA via thermally treating polyvinyl alcohol, and immobilization of TiO2 sol and C-PVA on CHC. By detecting the change of UV–vis absorption spectra of the model organic pollutant（methyl orange（MO）） in the presence of the composite under visible light irradiation, the photo-catalytic activity was evaluated and the results show that the CHC/C-PVA/TiO2 composite has an enhanced photo-catalytic activity when compared to the CHC/TiO2 composite. Besides, the CHC/C-PVA/TiO2 shows a good photo-catalytic stability after the fourth cycles. The structure analyses by scanning electron microscope（SEM） and energy dispersive X-ray spectroscopy（EDS） show the coexistence of C-PVA and TiO2 on the CHC and the cracks on the surface of CHC/C-PVA/TiO2. Result of ultraviolet-visible diffuse reflection spectroscopy（UV–vis DRS） reveals that the CHC/C-PVA/TiO2 can absorb both ultraviolet and visible light while result of X-ray photoelectron spectroscopy（XPS） indicates the existence of C, O and Ti elements in the CHC/C-PVA/TiO2. The typical structures as well as the optical characteristics of the CHC/C-PVA/TiO2 are responsible for the enhancement in the photo-catalytic activity.展开更多
基金supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(No.2020R1I1A1A01072161)and under the framework of the International Cooperation Program managed by NRF(No.2017K2A9A2A10013104)supported by the NRF grant funded by the Korea government(MSIP)(No.NRF-2020R1A2C3008671).
文摘The exfoliation of bulk graphitic carbon nitride(g-C_(3)N_(4))into monolayer has been intensively studied to induce maximum sur-face area for fundamental studies,but ended in failure to realize chemi-cally and physically well-defined monolayer of g-C_(3)N_(4)mostly due to the difficulty in reducing the layer thickness down to an atomic level.It has,therefore,remained as a challenging issue in two-dimensional(2D)chemistry and physics communities.In this study,an“atomic monolayer of g-C_(3)N_(4)with perfect two-dimensional limit”was successfully prepared by the chemically well-defined two-step routes.The atomically resolved monolayer of g-C_(3)N_(4)was also confirmed by spectroscopic and micro-scopic analyses.In addition,the experimental Cs-HRTEM image was collected,for the first time,which was in excellent agreement with the theoretically simulated;the evidence of monolayer of g-C_(3)N_(4)in the perfect 2D limit becomes now clear from the HRTEM image of orderly hexagonal symmetry with a cavity formed by encirclement of three adjacent heptazine units.Compared to bulk g-C_(3)N_(4),the present g-C_(3)N_(4)monolayer showed significantly higher photocatalytic gen-eration of H2O2 and H2,and electrocatalytic oxygen reduction reaction.In addition,its photocatalytic efficiency for H2O2 production was found to be the best for any known g-C_(3)N_(4)nanomaterials,underscoring the remarkable advantage of monolayer formation in optimizing the catalyst performance of g-C_(3)N_(4).
基金This work was supported by the National Key Basic Research Project of China (No. 2001CCA03600).
文摘Pd-MoO3/SiO2 catalyst has been prepared using the method of incipient wetness impregnation. The photo absorbing behaviors and chemisorbing properties of the catalyst have been characterized by UV-vis spectra and TPD-MS experiments. The results indicated that metal Pd loaded on MoOa/SiO2 has a significant effect on the photo absorbing performance of MoOa/SiO2, and an obvious blue shift of the absorption edge is produced. Under UV irradiation, the chemisorption state of CO2 undergoes decomposing process to form CO at 481 K, and a two-site adsorption state of ethane can be formed at around 496 K. Photo-oxidation of ethane using carbon dioxide can mainly produce propanal, ethanol and acetaldehyde in the temperature range of 353-423 K. The presence of metal Pd improves the catalytic activity remarkably.
基金financial support provided by the National Natural Science Foundation of China(21676078)the Natural Science Foundation of Hunan Province for Distinguished Young Scholar(2016JJ1013)+1 种基金Scientific Research Fund of Hunan Provincial Education Department(19A323)Science and Technology Planning Project of Hunan Province(2018TP1017)。
文摘Graphitic carbon nitride(g-C_(3)N_(4)) is a fascinating photocatalyst for solar energy utilization in photo-catalysis.Nevertheless,it often suffers from moderate photo-catalytic activity due to its low specific surface area and fast recombination rate of photogenerated electrons upon photo-excitation.Herein,we overcome the bottlenecks by constructing a porous g-C_(3)N_(4) nanosheet(PCNS)through a simple thermal oxidation etching method.Benefited from its porous layer structure,the obtained PCNS exhibits large specific surface area,efficient separation of photogenerated charge carriers,as well as high exposure of active sites.As a result,it is robust and universal in visible light-driven dehydrogenation of alcohols in water under oxidant-free condition.Almost quantitative yields(>99%)of various valuable carbonyl compounds were obtained over PCNS,while bulk g-C_(3)N_(4) was far less efficient.Moreover,the photo-catalyst was highly stable and could be facilely recovered from the aqueous system for efficient reuse.The easy preparation and excellent performance made PCNS a promising and competitive photocatalyst for the solar applications.
基金the National Natural Science Foundation of China(Grant nos.50573052 and 51173116)for supporting this research
文摘A novel visible light active photo-catalyst named CHC/C-PVA/TiO2, the composite of titanium dioxide（TiO2）with conjugated derivative of polyvinyl alcohol（C-PVA） loaded on a cordierite honeycomb ceramic（CHC）substrate, was fabricated by combining the synthesis of TiO2 sol, preparation of C-PVA via thermally treating polyvinyl alcohol, and immobilization of TiO2 sol and C-PVA on CHC. By detecting the change of UV–vis absorption spectra of the model organic pollutant（methyl orange（MO）） in the presence of the composite under visible light irradiation, the photo-catalytic activity was evaluated and the results show that the CHC/C-PVA/TiO2 composite has an enhanced photo-catalytic activity when compared to the CHC/TiO2 composite. Besides, the CHC/C-PVA/TiO2 shows a good photo-catalytic stability after the fourth cycles. The structure analyses by scanning electron microscope（SEM） and energy dispersive X-ray spectroscopy（EDS） show the coexistence of C-PVA and TiO2 on the CHC and the cracks on the surface of CHC/C-PVA/TiO2. Result of ultraviolet-visible diffuse reflection spectroscopy（UV–vis DRS） reveals that the CHC/C-PVA/TiO2 can absorb both ultraviolet and visible light while result of X-ray photoelectron spectroscopy（XPS） indicates the existence of C, O and Ti elements in the CHC/C-PVA/TiO2. The typical structures as well as the optical characteristics of the CHC/C-PVA/TiO2 are responsible for the enhancement in the photo-catalytic activity.
