由于氮原子和均匀孔隙的存在,二维石墨氮化碳被认为可用于电池电极材料。作为一种新型的多孔结构,g-C_2N材料在电池电极材料方面应用的研究甚少。本文通过第一性原理计算研究了单层g-C_2N上锂和钠的吸附和存储情况。基于单层g-C_2N的锂...由于氮原子和均匀孔隙的存在,二维石墨氮化碳被认为可用于电池电极材料。作为一种新型的多孔结构,g-C_2N材料在电池电极材料方面应用的研究甚少。本文通过第一性原理计算研究了单层g-C_2N上锂和钠的吸附和存储情况。基于单层g-C_2N的锂离子电池的容量可以达到596 mAh/g(LiC_2N),而相应的钠离子容量只能达到276 mAh/g (NaC_4N_2)。平均锂结合能相对于孤立的锂原子高达2. 39 e V,这表明g-C_2N上获得的锂电池容量在循环过程中可能不会持续。通过改变C和N原子之间的比例,在C∶N为5∶1的情况下,平均锂结合能可以降低到1. 69 e V,这说明在保持可逆电池容量的同时,循环性能显著改善。所有这些理论计算表明,具有均匀孔隙的石墨碳氮化物可能是一种具有高容量和锂迁移率的电极材料。展开更多
Understanding the performance of reactive oxygen species(ROS)in photocatalysis is pivotal for advancing their application in environmental remediation.However,techniques for investigating the generation and transforma...Understanding the performance of reactive oxygen species(ROS)in photocatalysis is pivotal for advancing their application in environmental remediation.However,techniques for investigating the generation and transformation mechanism of ROS have been largely overlooked.In this study,considering g‐C3N4 to be a model photocatalyst,we have focused on the ROS generation and transformation for efficient photocatalytic NO removal.It was found that the key to improving the photocatalysis performance was to enhance the ROS transformation from·O2^-to·OH,elevating the production of·OH.The ROS directly participate in the photocatalytic NO removal and tailor the rate‐determining step,which is required to overcome the high activation energy of the intermediate conversion.Using a closely combined experimental and theoretical method,this work provides a new protocol to investigate the ROS behavior on g‐C3N4 for effective NO removal and clarifies the reaction mechanism at the atomic level,which enriches the understanding of ROS in photocatalytic environmental remediation.展开更多
A facile approach to the preparation of a novel magnetically separable H_5PMo_（10）V_2O_（40）/Fe_3O_4/g-C_3N_4（PMoV/Fe_3O_4/g-C_3N_4） nanocomposite by chemical impregnation is demonstrated.The prepared nanocomposi...A facile approach to the preparation of a novel magnetically separable H_5PMo_（10）V_2O_（40）/Fe_3O_4/g-C_3N_4（PMoV/Fe_3O_4/g-C_3N_4） nanocomposite by chemical impregnation is demonstrated.The prepared nanocomposite was characterized and its acidity was measured by potentiometric titration.PMoV/Fe_3O_4/g-C_3N_4 showed high catalytic activity in the selective oxidative desulfurization of sulfides to their corresponding sulfoxides or sulfones.The catalytic oxidation of a dibenzothiophene（DBT）-containing model oil and that of real oil were also studied under optimized conditions.In addition,the effects of various nitrogen compounds,as well as the use of one- and two-ring aromatic hydrocarbons as co-solvents,on the catalytic removal of sulfur from DBT were investigated.The catalyst was easily separated and could be recovered from the reaction mixture by using an external magnetic field.Additionally,the remaining reactants could be separated from the products by simple decantation if an appropriate solvent was chosen for the extraction.The advantages of this nanocatalyst are its high catalytic activity and reusability;it can be used at least four times without considerable loss of activity.展开更多
As one of the most appealing and attractive technologies, photocatalysis is widely used as a promising method to circumvent the environmental and energy problems. Due to its chemical stability and unique physicochemic...As one of the most appealing and attractive technologies, photocatalysis is widely used as a promising method to circumvent the environmental and energy problems. Due to its chemical stability and unique physicochemical, graphitic carbon nitride (g-C3N4) has become research hotspots in the community. However, g-C3N4 photocatalyst still suffers from many problems, resulting in unsatisfactory photocatalytic activity such as low specific surface area, high charge recombination and insufficient visible light utilization. Since 2009, g-C3N4-based heterostructures have attracted the attention of scientists worldwide for their greatly enhanced photocatalytic performance. Overall, this review summarizes the recent advances of g-C3N4-based nanocomposites modified with transition metal sulfide (TMS), including (1) preparation of pristine g-C3N4,(2) modification strategies of g-C3N4,(3) design principles of TMS-modified g-C3N4 heterostructured photocatalysts, and (4) applications in energy conversion. What is more, the characteristics and transfer mechanisms of each classification of the metal sulfide heterojunction system will be critically reviewed, spanning from the following categories:(1) Type I heterojunction,(2) Type II heterojunction,(3) p-n heterojunction,(4) Schottky junction and (5) Z-scheme heterojunction. Apart from that, the application of g-C3N4-based heterostructured photocatalysts in H2 evolution, CO2 reduction, N2 fixation and pollutant degradation will also be systematically presented. Last but not least, this review will conclude with invigorating perspectives, limitations and prospects for further advancing g-C3N4-based heterostructured photocatalysts toward practical benefits for a sustainable future.展开更多
Ultrathin graphitic carbon nitride nanoplatelets （UGCNPs） are synthesized by a facile manner via an efficient and eco-friendly ball milling approach. The obtained UGCNPs are 2-6 nm in size and 0.35-0.7 nm in thickne...Ultrathin graphitic carbon nitride nanoplatelets （UGCNPs） are synthesized by a facile manner via an efficient and eco-friendly ball milling approach. The obtained UGCNPs are 2-6 nm in size and 0.35-0.7 nm in thickness, with improved specific surface area over that of bulk graphitic carbon nitride. Photochemical experiments show that the UGCNPs are highly active in visible-light water splitting, with a hydrogen evolution rate of 1,365 μmol·h^-1·g^-1, which is 13.7-fold greater than that of their bulk counterparts. The notable improvement in the hydrogen evolution rate observed with UGCNPs under visible light is due to the synergistic effects derived from the increased specific surface area, reduced thickness, and a negative shift in the conduction band concomitant with the exfoliation of bulk graphitic carbon nitride into UGCNPs. In addition to metal- free visible-light-driven photocatalytic hydrogen production, the UGCNPs find attractive applications in biomedical imaging and optoelectronics because of their superior luminescence characteristics.展开更多
Covalent functionalization of graphene offers opportunities for tailoring its properties and is an unavoidable consequence of some graphene synthesis techniques. However, the changes induced by the functionalization a...Covalent functionalization of graphene offers opportunities for tailoring its properties and is an unavoidable consequence of some graphene synthesis techniques. However, the changes induced by the functionalization are not well understood. By using atomic sources to control the extent of the oxygen and nitrogen functionalization, we studied the evolution in the structure and properties at the atomic scale. Atomic oxygen reversibly introduces epoxide groups whilst, under similar conditions, atomic nitrogen irreversibly creates diverse functionalities including substitutional, pyridinic, and pyrrolic nitrogen. Atomic oxygen leaves the Fermi energy at the Dirac point （i.e., undoped）, whilst atomic nitrogen results in a net n-doping; however, the experimental results are consistent with the dominant electronic effect for both being a transition from delocalized to localized states, and hence the loss of the signature electronic structure of graphene.展开更多
In this paper,we demonstrate the conversion of graphene oxide(GO) into boron carbon oxynitride(BCNO) hybrid nanosheets via a reaction with boric acid and urea,during which the boron and nitrogen atoms are incorporated...In this paper,we demonstrate the conversion of graphene oxide(GO) into boron carbon oxynitride(BCNO) hybrid nanosheets via a reaction with boric acid and urea,during which the boron and nitrogen atoms are incorporated into graphene nanosheets.The experimental results reveal that GO is important for the photoluminescence(PL) BCNO phosphor particles.More importantly,in this system,the prepared BCNO phosphors can be used to prepare the materials needed for red light emitting diodes(LEDs).展开更多
文摘由于氮原子和均匀孔隙的存在,二维石墨氮化碳被认为可用于电池电极材料。作为一种新型的多孔结构,g-C_2N材料在电池电极材料方面应用的研究甚少。本文通过第一性原理计算研究了单层g-C_2N上锂和钠的吸附和存储情况。基于单层g-C_2N的锂离子电池的容量可以达到596 mAh/g(LiC_2N),而相应的钠离子容量只能达到276 mAh/g (NaC_4N_2)。平均锂结合能相对于孤立的锂原子高达2. 39 e V,这表明g-C_2N上获得的锂电池容量在循环过程中可能不会持续。通过改变C和N原子之间的比例,在C∶N为5∶1的情况下,平均锂结合能可以降低到1. 69 e V,这说明在保持可逆电池容量的同时,循环性能显著改善。所有这些理论计算表明,具有均匀孔隙的石墨碳氮化物可能是一种具有高容量和锂迁移率的电极材料。
基金the National Natural Science Foundation of China(51508356)Science and Technology Support Program of Sichuan Province(2014GZ0213,2016GZ0045)Youth Project in Science and Technology Innovation Program of Sichuan Province(17-YCG053)~~
文摘Understanding the performance of reactive oxygen species(ROS)in photocatalysis is pivotal for advancing their application in environmental remediation.However,techniques for investigating the generation and transformation mechanism of ROS have been largely overlooked.In this study,considering g‐C3N4 to be a model photocatalyst,we have focused on the ROS generation and transformation for efficient photocatalytic NO removal.It was found that the key to improving the photocatalysis performance was to enhance the ROS transformation from·O2^-to·OH,elevating the production of·OH.The ROS directly participate in the photocatalytic NO removal and tailor the rate‐determining step,which is required to overcome the high activation energy of the intermediate conversion.Using a closely combined experimental and theoretical method,this work provides a new protocol to investigate the ROS behavior on g‐C3N4 for effective NO removal and clarifies the reaction mechanism at the atomic level,which enriches the understanding of ROS in photocatalytic environmental remediation.
基金the Razi University Research Council for support of this work
文摘A facile approach to the preparation of a novel magnetically separable H_5PMo_（10）V_2O_（40）/Fe_3O_4/g-C_3N_4（PMoV/Fe_3O_4/g-C_3N_4） nanocomposite by chemical impregnation is demonstrated.The prepared nanocomposite was characterized and its acidity was measured by potentiometric titration.PMoV/Fe_3O_4/g-C_3N_4 showed high catalytic activity in the selective oxidative desulfurization of sulfides to their corresponding sulfoxides or sulfones.The catalytic oxidation of a dibenzothiophene（DBT）-containing model oil and that of real oil were also studied under optimized conditions.In addition,the effects of various nitrogen compounds,as well as the use of one- and two-ring aromatic hydrocarbons as co-solvents,on the catalytic removal of sulfur from DBT were investigated.The catalyst was easily separated and could be recovered from the reaction mixture by using an external magnetic field.Additionally,the remaining reactants could be separated from the products by simple decantation if an appropriate solvent was chosen for the extraction.The advantages of this nanocatalyst are its high catalytic activity and reusability;it can be used at least four times without considerable loss of activity.
基金supported by Xiamen University Malaysia Research Fund (XMUMRF/2019-C3/IENG/0013)financial assistance and faculty start-up grants/supports from Xiamen University~~
文摘As one of the most appealing and attractive technologies, photocatalysis is widely used as a promising method to circumvent the environmental and energy problems. Due to its chemical stability and unique physicochemical, graphitic carbon nitride (g-C3N4) has become research hotspots in the community. However, g-C3N4 photocatalyst still suffers from many problems, resulting in unsatisfactory photocatalytic activity such as low specific surface area, high charge recombination and insufficient visible light utilization. Since 2009, g-C3N4-based heterostructures have attracted the attention of scientists worldwide for their greatly enhanced photocatalytic performance. Overall, this review summarizes the recent advances of g-C3N4-based nanocomposites modified with transition metal sulfide (TMS), including (1) preparation of pristine g-C3N4,(2) modification strategies of g-C3N4,(3) design principles of TMS-modified g-C3N4 heterostructured photocatalysts, and (4) applications in energy conversion. What is more, the characteristics and transfer mechanisms of each classification of the metal sulfide heterojunction system will be critically reviewed, spanning from the following categories:(1) Type I heterojunction,(2) Type II heterojunction,(3) p-n heterojunction,(4) Schottky junction and (5) Z-scheme heterojunction. Apart from that, the application of g-C3N4-based heterostructured photocatalysts in H2 evolution, CO2 reduction, N2 fixation and pollutant degradation will also be systematically presented. Last but not least, this review will conclude with invigorating perspectives, limitations and prospects for further advancing g-C3N4-based heterostructured photocatalysts toward practical benefits for a sustainable future.
基金This project is sponsored by NSFC （Nos. 21325415, 21174019, 21301018, 51161120361）, National Basic Research Program of China （2011CB013000）, Basic Research Foundation of Beijing Institute of Technology （20121942008）, Fok Ying Tong Education Foundation （No. 131043）, the 111 Project B07012, Beijing Natural Science Foundation （2152028） and the Beijing Key Laboratory for Chemical Power Source and Green Catalysis under the contract no. 2013CX02031.
文摘Ultrathin graphitic carbon nitride nanoplatelets （UGCNPs） are synthesized by a facile manner via an efficient and eco-friendly ball milling approach. The obtained UGCNPs are 2-6 nm in size and 0.35-0.7 nm in thickness, with improved specific surface area over that of bulk graphitic carbon nitride. Photochemical experiments show that the UGCNPs are highly active in visible-light water splitting, with a hydrogen evolution rate of 1,365 μmol·h^-1·g^-1, which is 13.7-fold greater than that of their bulk counterparts. The notable improvement in the hydrogen evolution rate observed with UGCNPs under visible light is due to the synergistic effects derived from the increased specific surface area, reduced thickness, and a negative shift in the conduction band concomitant with the exfoliation of bulk graphitic carbon nitride into UGCNPs. In addition to metal- free visible-light-driven photocatalytic hydrogen production, the UGCNPs find attractive applications in biomedical imaging and optoelectronics because of their superior luminescence characteristics.
文摘Covalent functionalization of graphene offers opportunities for tailoring its properties and is an unavoidable consequence of some graphene synthesis techniques. However, the changes induced by the functionalization are not well understood. By using atomic sources to control the extent of the oxygen and nitrogen functionalization, we studied the evolution in the structure and properties at the atomic scale. Atomic oxygen reversibly introduces epoxide groups whilst, under similar conditions, atomic nitrogen irreversibly creates diverse functionalities including substitutional, pyridinic, and pyrrolic nitrogen. Atomic oxygen leaves the Fermi energy at the Dirac point （i.e., undoped）, whilst atomic nitrogen results in a net n-doping; however, the experimental results are consistent with the dominant electronic effect for both being a transition from delocalized to localized states, and hence the loss of the signature electronic structure of graphene.
基金supported by the National Natural Science Foundation of China(No.11404397)
文摘In this paper,we demonstrate the conversion of graphene oxide(GO) into boron carbon oxynitride(BCNO) hybrid nanosheets via a reaction with boric acid and urea,during which the boron and nitrogen atoms are incorporated into graphene nanosheets.The experimental results reveal that GO is important for the photoluminescence(PL) BCNO phosphor particles.More importantly,in this system,the prepared BCNO phosphors can be used to prepare the materials needed for red light emitting diodes(LEDs).
