The copolymerizations of ethylene with 1-hexene or 1-0ctene by using TiC14/MgCI2/THF catalysts modified with different metal halide additives （ZnCI2, SIC14, and the combined ZnC12-SiCl4） were investigated based on c...The copolymerizations of ethylene with 1-hexene or 1-0ctene by using TiC14/MgCI2/THF catalysts modified with different metal halide additives （ZnCI2, SIC14, and the combined ZnC12-SiCl4） were investigated based on catalytic activity and copolymer properties. It was found that the catalyst modified with mixed ZnC12-SiC14 revealed the highest activities for both ethylene/1-hexene and ethylene/1-0ctene copolymerization. The increase in activities was due to the formation of acidic sites by modifying the catalysts with Lewis acids. Based on the FTIR measurements, the characteristic C--O--C peaks of the catalysts modified with metal halide additives were slightly shifted to lower wavenumber when compared to the unmodified catalyst. This showed that the modified catalysts could generate more acid sites in the TiC14/MgC12/THF catalytic system leading to an increase in activities as well as comonomer insertion （as proven by IaC-NMR）. However, Lewis acid- modifications did not affect the microstructure of the copolymers obtained. By comparison on the properties of copolymers prepared with the unmodified catalyst, it was found that polymers with ZnC12 and/or SIC14 modification exhibited a slight decrease in melting temperature, crystallinity and density. It is suggested that these results were obtained based on the different amount of ct-olefins insertion, regardless of the types of Lewis acids and comonomer.展开更多
MXenes,drawn from MAX phases,are special two-dimensional substances with numerous advantages in nonlinear optics,specifically in giant and ultrashort pulsed-laser applications.Ti_(3)C_(2)T_(x)and Ti_(2)CT_(x)nanosheet...MXenes,drawn from MAX phases,are special two-dimensional substances with numerous advantages in nonlinear optics,specifically in giant and ultrashort pulsed-laser applications.Ti_(3)C_(2)T_(x)and Ti_(2)CT_(x)nanosheets however rapidly deteriorate under ambient conditions,limiting their applications.This paper demonstrates how excellent modulation depth of one of the MAX phase compounds vanadium zinc carbide(V_2ZnC)makes it a brilliant saturable absorber(SA)in passively Q-switched all-fiber pulsed lasers,integrated such that a 16.73-μm V_(2)ZnC-polyvinyl alcohol(PVA)thin film acts as SA in the laser.Saturable and non-saturable absorptions were found to be 13.2%and 10.47%,while saturation optical intensity and modulation depth were 6.25 k W/cm^(2)and 12.43%,respectively,illustrating the optical nonlinearity.The superiority of MAX-PVA,fabricated in four distinct ratios,was demonstrated by the fact that it self-starts a giant pulsed laser at pump power as low as 22.5 mW and firmly accomplished 120.6 kHz repetition rate with a pulse width of 2.08μs.It is a fine SA for the use of pulsed-laser production using all-fiber laser due to fabrication simplicity and great optical,thermophysical,and mechanical qualities.展开更多
Bimetallic carbide electrocatalysts have great potential to outperform well-defined single metal ones for the electrochemical hydrogen evolution reaction(HER).However,the lack of regulation tactics of electronic struc...Bimetallic carbide electrocatalysts have great potential to outperform well-defined single metal ones for the electrochemical hydrogen evolution reaction(HER).However,the lack of regulation tactics of electronic structures largely impedes the upgrading of bimetallic carbides for efficient hydrogen evolution.Herein,a novel Ni_(3)ZnC_(0.7)/Ni heterostructure embedded in N-doped carbon nanotubes(Ni_(3)ZnC_(0.7)/Ni@CNTs)was synthesized by a facile one-step pyrolysis protocol.Experimental and theoretical results demonstrated that the electronic coupling interaction between Ni and Ni_(3)ZnC_(0.7) triggered the redistribution of interfacial charge and optimized the electronic state density of metallic Ni sites,which reduced the H^(*) adsorption–desorption energy barrier and thus accelerated the HER kinetics in the electrocatalytic process.The resulting Ni_(3)ZnC_(0.7)/Ni@CNTs required ultralow overpotentials of 93 and 256 mV to deliver current densities of 10 and 100 mA cm^(−2) for the HER,respectively,and exhibited extraordinary long-term durability for at least 400 h in 1.0 M KOH solution.This work provides a novel perspective for the design of high-performance bimetallic carbide electrocatalysts for water splitting.展开更多
基金financially supported by the Dusadeepipat scholarship at Graduate school of Chulalongkorn Universitythe Thailand Research Fund(TRF)+1 种基金the Higher Education Promotion and National Research University Development(AM1088A)the office of the Higher Education Commission(CHE)
文摘The copolymerizations of ethylene with 1-hexene or 1-0ctene by using TiC14/MgCI2/THF catalysts modified with different metal halide additives （ZnCI2, SIC14, and the combined ZnC12-SiCl4） were investigated based on catalytic activity and copolymer properties. It was found that the catalyst modified with mixed ZnC12-SiC14 revealed the highest activities for both ethylene/1-hexene and ethylene/1-0ctene copolymerization. The increase in activities was due to the formation of acidic sites by modifying the catalysts with Lewis acids. Based on the FTIR measurements, the characteristic C--O--C peaks of the catalysts modified with metal halide additives were slightly shifted to lower wavenumber when compared to the unmodified catalyst. This showed that the modified catalysts could generate more acid sites in the TiC14/MgC12/THF catalytic system leading to an increase in activities as well as comonomer insertion （as proven by IaC-NMR）. However, Lewis acid- modifications did not affect the microstructure of the copolymers obtained. By comparison on the properties of copolymers prepared with the unmodified catalyst, it was found that polymers with ZnC12 and/or SIC14 modification exhibited a slight decrease in melting temperature, crystallinity and density. It is suggested that these results were obtained based on the different amount of ct-olefins insertion, regardless of the types of Lewis acids and comonomer.
基金supported by the Ministry of Higher under Fundamental Research Grant Scheme(No.FRGS/1/2020/TK0/UTM/02/46)Nippon Sheet Glass Grant(No.R.K130000.7343.4B818)。
文摘MXenes,drawn from MAX phases,are special two-dimensional substances with numerous advantages in nonlinear optics,specifically in giant and ultrashort pulsed-laser applications.Ti_(3)C_(2)T_(x)and Ti_(2)CT_(x)nanosheets however rapidly deteriorate under ambient conditions,limiting their applications.This paper demonstrates how excellent modulation depth of one of the MAX phase compounds vanadium zinc carbide(V_2ZnC)makes it a brilliant saturable absorber(SA)in passively Q-switched all-fiber pulsed lasers,integrated such that a 16.73-μm V_(2)ZnC-polyvinyl alcohol(PVA)thin film acts as SA in the laser.Saturable and non-saturable absorptions were found to be 13.2%and 10.47%,while saturation optical intensity and modulation depth were 6.25 k W/cm^(2)and 12.43%,respectively,illustrating the optical nonlinearity.The superiority of MAX-PVA,fabricated in four distinct ratios,was demonstrated by the fact that it self-starts a giant pulsed laser at pump power as low as 22.5 mW and firmly accomplished 120.6 kHz repetition rate with a pulse width of 2.08μs.It is a fine SA for the use of pulsed-laser production using all-fiber laser due to fabrication simplicity and great optical,thermophysical,and mechanical qualities.
基金supported by the National Natural Science Foundation of China(No.22179074,U22A20144,52073166 and 52172049)the Program for International S&T Cooperation Projects of Shaanxi Province(2020GHJD-04 and 2023GHZD-08)+4 种基金the Scientific Research Project of Education Department of Shaanxi Province(No.22JK0297)the Doctoral Scientific Research Startup Foundation of Shaanxi University of Science and Technology(2016QNBT-07)the Open Foundation of Key Laboratory of Auxiliary Chemistry and Technology for Chemical Industry,Ministry of Education,Shaanxi University of Science and Technology(No.KFKT2023-01)Shaanxi Collaborative Innovation Center of Industrial Auxiliary Chemistry and Technology,Shaanxi University of Science and Technology(No.KFKT2023-01)the Young Talent Fund of Xi’an Association for Science and Technology.
文摘Bimetallic carbide electrocatalysts have great potential to outperform well-defined single metal ones for the electrochemical hydrogen evolution reaction(HER).However,the lack of regulation tactics of electronic structures largely impedes the upgrading of bimetallic carbides for efficient hydrogen evolution.Herein,a novel Ni_(3)ZnC_(0.7)/Ni heterostructure embedded in N-doped carbon nanotubes(Ni_(3)ZnC_(0.7)/Ni@CNTs)was synthesized by a facile one-step pyrolysis protocol.Experimental and theoretical results demonstrated that the electronic coupling interaction between Ni and Ni_(3)ZnC_(0.7) triggered the redistribution of interfacial charge and optimized the electronic state density of metallic Ni sites,which reduced the H^(*) adsorption–desorption energy barrier and thus accelerated the HER kinetics in the electrocatalytic process.The resulting Ni_(3)ZnC_(0.7)/Ni@CNTs required ultralow overpotentials of 93 and 256 mV to deliver current densities of 10 and 100 mA cm^(−2) for the HER,respectively,and exhibited extraordinary long-term durability for at least 400 h in 1.0 M KOH solution.This work provides a novel perspective for the design of high-performance bimetallic carbide electrocatalysts for water splitting.
