Polarization-dependent loss is important to the highly electromagnetic wave absorption(EWA)performance.Recently,metal–Nx moieties have been discovered to trigger polarization loss,but the physical origin and other po...Polarization-dependent loss is important to the highly electromagnetic wave absorption(EWA)performance.Recently,metal–Nx moieties have been discovered to trigger polarization loss,but the physical origin and other possible related loss mechanisms still need to be deeply explored.In this article,we reveal that the FeN_(4)moiety from iron phthalocyanine(FePc)can coordinate with Ti_(3)C_(2)T_(x)through Ti–OH groups,inducing dipole polarization and synchronous magnetic modulation in Fe/TiO_(2)/Ti_(3)C_(2)T_(x)composites.Interestingly,using the enhanced electric dipole moment and increased number of unpaired electrons in Fe atoms,the dipole polarization loss and possible magnetic response can be rapidly confirmed and evaluated.As a result,the minimum reflection loss(RLmin)of Fe/TiO_(2)/Ti_(3)C_(2)T_(x)composites reaches−67.12 dB at 6.72 GHz with a thickness of 3.32 mm.This study elaborates the EWA mechanism based on the atomic scale,and provides a new idea to design efficient EWA materials.展开更多
Rational regulation on pore structure and active site density plays critical roles in enhancing the performance of Fe-N-C catalysts. As the microporous structure of the carbon substrate is generally regarded as the ac...Rational regulation on pore structure and active site density plays critical roles in enhancing the performance of Fe-N-C catalysts. As the microporous structure of the carbon substrate is generally regarded as the active site hosts, its hostility to electron/mass transfer could lead to the incomplete fulfillment of the catalytic activity. Besides, the formation of inactive metallic Fe particles during the conventional catalyst synthesis could also decrease the active site density and complicate the identification of real active site. Herein, we developed a facial hydrogen etching methodology to yield single site Fe-N-C catalysts featured with micro/mesoporous hierarchical structure. The hydrogen concentration in pyrolysis process was designated to effectively regulate the pore structure and active site density of the resulted catalysts.The optimized sample achieves excellent ORR catalytic performance with an ultralow H2O2 yield(1%)and superb stability over 10,000 cycles. Our finding provides new thoughts for the rational design of hierarchically porous carbon-based materials and highly promising non-precious metal ORR catalysts.展开更多
Pyrolyzed Fe-Nx/C materials derived from Fe-doped ZIF-8 are recently emerged as promising alternativesto noble metal platinum-based catalysts towards oxygen reduction reaction （ORR） and elucidating the de-pendacne o...Pyrolyzed Fe-Nx/C materials derived from Fe-doped ZIF-8 are recently emerged as promising alternativesto noble metal platinum-based catalysts towards oxygen reduction reaction （ORR） and elucidating the de-pendacne of Fe source on the active site structure and final ORR performance is highly desirbale for fur-ther development of these materials. Here, we designed and synthesized a series of Fe-N-C catalysts usingZIF-8 and various iron salts （Fe（acac）3, FeCI3, Fe（NO3）3） as precusors. We found that the iron precursors,mainly the molecular size, hydrolysis extent, do play a major role in determining the final morphology ofFe, namely forming the Fe-Nx coordination or Fe3C nanoparticles, as well as the site density, therefore,significantly affecting the ORR activity. Among the three iron sources, Fe（acac）3 is most advantageous tothe preferential formation of single-atom Fe-Nx active sites and the derived catalyst demonstrated bestORR performance.展开更多
The novel Fe-N co-doped ordered mesoporous carbon with high catalytic activity in m-cresol removal was prepared by urea-assisted impregnation and simple pyrolysis method.During the preparation of the Fe-NC catalyst,th...The novel Fe-N co-doped ordered mesoporous carbon with high catalytic activity in m-cresol removal was prepared by urea-assisted impregnation and simple pyrolysis method.During the preparation of the Fe-NC catalyst,the complexation of N elements in urea could anchor Fe,and the formation of C3N4during urea pyrolysis could also prevent migration and aggregation of Fe species,which jointly improve the dispersion and stability of Fe.The FeN4sites and highly dispersed Fe nanoparticles synergistically trigger the dual-site peroxymonosulfate (PMS) activation for highly efficient m-cresol degradation,while the ordered mesoporous structure of the catalyst could improve the mass transfer rate of the catalytic process,which together promote catalytic degradation of m-cresol by PMS activation.Reactive oxygen species (ROS) analytic experiments demonstrate that the system degrades m-cresol by free radical pathway mainly based on SO_(4)^(-)·and·OH,and partially based on·OH as the active components,and a possible PMS activation mechanism by 5Fe-50 for m-cresol degradation was proposed.This study can provide theoretical guidance for the preparation of efficient and stable catalysts for the degradation of organic pollutants by activated PMS.展开更多
基金supported by the Taishan Young Scholar Program(tsqn202306267)the National Natural Science Foundation of China(51802168)the Natural Science Foundation of Shandong Province(ZR2024ME182,ZR2021ME122)。
文摘Polarization-dependent loss is important to the highly electromagnetic wave absorption(EWA)performance.Recently,metal–Nx moieties have been discovered to trigger polarization loss,but the physical origin and other possible related loss mechanisms still need to be deeply explored.In this article,we reveal that the FeN_(4)moiety from iron phthalocyanine(FePc)can coordinate with Ti_(3)C_(2)T_(x)through Ti–OH groups,inducing dipole polarization and synchronous magnetic modulation in Fe/TiO_(2)/Ti_(3)C_(2)T_(x)composites.Interestingly,using the enhanced electric dipole moment and increased number of unpaired electrons in Fe atoms,the dipole polarization loss and possible magnetic response can be rapidly confirmed and evaluated.As a result,the minimum reflection loss(RLmin)of Fe/TiO_(2)/Ti_(3)C_(2)T_(x)composites reaches−67.12 dB at 6.72 GHz with a thickness of 3.32 mm.This study elaborates the EWA mechanism based on the atomic scale,and provides a new idea to design efficient EWA materials.
基金supported by the National Natural Science Foundation of China(21633008,21433003,U1601211,21733004)National Science and Technology Major Project(2016YFB0101202)+1 种基金Jilin Province Science and Technology Development Program(20150101066JC,20160622037JC,20170203003SF,20170520150JH)Hundred Talents Program of Chinese Academy of Sciences and the Recruitment Program of Foreign Experts(WQ20122200077)
文摘Rational regulation on pore structure and active site density plays critical roles in enhancing the performance of Fe-N-C catalysts. As the microporous structure of the carbon substrate is generally regarded as the active site hosts, its hostility to electron/mass transfer could lead to the incomplete fulfillment of the catalytic activity. Besides, the formation of inactive metallic Fe particles during the conventional catalyst synthesis could also decrease the active site density and complicate the identification of real active site. Herein, we developed a facial hydrogen etching methodology to yield single site Fe-N-C catalysts featured with micro/mesoporous hierarchical structure. The hydrogen concentration in pyrolysis process was designated to effectively regulate the pore structure and active site density of the resulted catalysts.The optimized sample achieves excellent ORR catalytic performance with an ultralow H2O2 yield(1%)and superb stability over 10,000 cycles. Our finding provides new thoughts for the rational design of hierarchically porous carbon-based materials and highly promising non-precious metal ORR catalysts.
基金supported by the National Natural Science Foundation of China(21633008,21433003,U1601211,21733004)National Science and Technology Major Project(2016YFB0101202)+2 种基金Jilin Province Science and Technology Development Program(20150101066JC,20160622037JC,20170203003SF,20170520150JH)Hundred Talents Program of Chinese Academy of Sciencesthe Recruitment Program of Foreign Experts(WQ20122200077)
文摘Pyrolyzed Fe-Nx/C materials derived from Fe-doped ZIF-8 are recently emerged as promising alternativesto noble metal platinum-based catalysts towards oxygen reduction reaction （ORR） and elucidating the de-pendacne of Fe source on the active site structure and final ORR performance is highly desirbale for fur-ther development of these materials. Here, we designed and synthesized a series of Fe-N-C catalysts usingZIF-8 and various iron salts （Fe（acac）3, FeCI3, Fe（NO3）3） as precusors. We found that the iron precursors,mainly the molecular size, hydrolysis extent, do play a major role in determining the final morphology ofFe, namely forming the Fe-Nx coordination or Fe3C nanoparticles, as well as the site density, therefore,significantly affecting the ORR activity. Among the three iron sources, Fe（acac）3 is most advantageous tothe preferential formation of single-atom Fe-Nx active sites and the derived catalyst demonstrated bestORR performance.
基金gratefully acknowledge the financial support of the National Natural Science Foundation of China(22108145 and 21978143)the Shandong Province Natural Science Foundation(ZR2020QB189)+1 种基金State Key Laboratory of Heavy Oil Processing(SKLHOP202203008)the Talent Foundation funded by Province and Ministry Co-construction Collaborative Innovation Center of Eco-chemical Engineering(STHGYX2201).
文摘The novel Fe-N co-doped ordered mesoporous carbon with high catalytic activity in m-cresol removal was prepared by urea-assisted impregnation and simple pyrolysis method.During the preparation of the Fe-NC catalyst,the complexation of N elements in urea could anchor Fe,and the formation of C3N4during urea pyrolysis could also prevent migration and aggregation of Fe species,which jointly improve the dispersion and stability of Fe.The FeN4sites and highly dispersed Fe nanoparticles synergistically trigger the dual-site peroxymonosulfate (PMS) activation for highly efficient m-cresol degradation,while the ordered mesoporous structure of the catalyst could improve the mass transfer rate of the catalytic process,which together promote catalytic degradation of m-cresol by PMS activation.Reactive oxygen species (ROS) analytic experiments demonstrate that the system degrades m-cresol by free radical pathway mainly based on SO_(4)^(-)·and·OH,and partially based on·OH as the active components,and a possible PMS activation mechanism by 5Fe-50 for m-cresol degradation was proposed.This study can provide theoretical guidance for the preparation of efficient and stable catalysts for the degradation of organic pollutants by activated PMS.
