Heteroatoms doped Fe-N-C electrocatalysts have been widely acknowledged as one of the most promising candidates to replace Pt-based materials for electrocatalyzing oxygen reduction reaction(ORR).However,the complicate...Heteroatoms doped Fe-N-C electrocatalysts have been widely acknowledged as one of the most promising candidates to replace Pt-based materials for electrocatalyzing oxygen reduction reaction(ORR).However,the complicated synthesis method and controversial catalytic mechanism represent a substantial impediment as of today.Herein,a very facile strategy to prepare Fe-N/S-C hybrid through pyrolyzing Zn and Fe bimetallic MOFs is rationally designed.The electrocatalytic ORR performance shows a volcanotype curve with the increment of added Fe content.The half-wave potential(E1/2) for ORR at optimized Fe-N/S-C-10%(10%=n(Fe)/(n(Fe)+n(Zn)),n(Fe) and n(Zn) represent the moles of Fe2+ and Zn2+ in the precursors,respectively) shifts significantly to the positive direction of 19.6 mV with respect to that of Pt/C in acidic media,as well as a high 4 e selectivity and methanol tolerance.After 10,000 potential cycles,E1/2 exhibits a small negative shift of-27.5 mV at Fe-N/S-C-10% compared favorably with Pt/C(~141.0 mV).This can be attributed to:(ⅰ) large specific surface area(849 m^(2)/g) and hierarchically porous structure are favorable for the rapid mass transfer and active sites exposure;(ⅱ) the embedded Fecontaining nanoparticles in porous carbon are difficult to be moved and further agglomerated during the electrochemical accelerated aging test,further improving its stability;(ⅲ) there exist small Fecontaining nanoparticles,uniformly doped N and S,abundant Fe-N as efficiently active sites.This work represents a breakthrough in the development of high-efficient non-precious-metal catalysts(NPMCs)to address the current Pt-based electrocatalysts challenges.展开更多
开展6 000和10 000 k N·m能级强夯的现场试验,以强夯前后多道瞬态面波测试和重型动力触探试验方法,对强夯处理效果进行测试。试验结果表明:强夯加固处理后地基承载力和土体工程特性得到改善,但地基承载力特征值和压缩模量局部深度...开展6 000和10 000 k N·m能级强夯的现场试验,以强夯前后多道瞬态面波测试和重型动力触探试验方法,对强夯处理效果进行测试。试验结果表明:强夯加固处理后地基承载力和土体工程特性得到改善,但地基承载力特征值和压缩模量局部深度仍不能满足设计要求;6 000和10 000 k N·m能级有效加固深度分别为6.0~7.0 m和7.0~8.0 m;10 000 k N·m能级试验区浅层加固处理效果较差,与浅层存在淤泥质土、夯坑回填方式及第3遍夯点间距过大和夯能过小等因素有关,需采取相应的处理措施。展开更多
基金financially supported by the National Natural Science Foundation of China (21978331, 21975292, 21905311)the National Key Research and Development Program of China (Program No. 2016YFB0101200 (2016YFB0101204))+5 种基金the Guangdong Basic and Applied Basic Research Foundation (2020A1515010343)the Guangzhou Science and Technology Project (201707010079)the fundamental Research Funds for Central Universities (No. 19lgpy136, 19lgpy116)the Tip-top Scientific and Technical Innovative Youth Talents of Guangdong special support program (No. 2016TQ03N322) for financial supportthe China Postdoctoral Science Foundation Grant (No. 2019M653142)the support of the startup grant of “Hundred Talents Program” in Sun Yat-sen University (No. 76110-18841219)。
文摘Heteroatoms doped Fe-N-C electrocatalysts have been widely acknowledged as one of the most promising candidates to replace Pt-based materials for electrocatalyzing oxygen reduction reaction(ORR).However,the complicated synthesis method and controversial catalytic mechanism represent a substantial impediment as of today.Herein,a very facile strategy to prepare Fe-N/S-C hybrid through pyrolyzing Zn and Fe bimetallic MOFs is rationally designed.The electrocatalytic ORR performance shows a volcanotype curve with the increment of added Fe content.The half-wave potential(E1/2) for ORR at optimized Fe-N/S-C-10%(10%=n(Fe)/(n(Fe)+n(Zn)),n(Fe) and n(Zn) represent the moles of Fe2+ and Zn2+ in the precursors,respectively) shifts significantly to the positive direction of 19.6 mV with respect to that of Pt/C in acidic media,as well as a high 4 e selectivity and methanol tolerance.After 10,000 potential cycles,E1/2 exhibits a small negative shift of-27.5 mV at Fe-N/S-C-10% compared favorably with Pt/C(~141.0 mV).This can be attributed to:(ⅰ) large specific surface area(849 m^(2)/g) and hierarchically porous structure are favorable for the rapid mass transfer and active sites exposure;(ⅱ) the embedded Fecontaining nanoparticles in porous carbon are difficult to be moved and further agglomerated during the electrochemical accelerated aging test,further improving its stability;(ⅲ) there exist small Fecontaining nanoparticles,uniformly doped N and S,abundant Fe-N as efficiently active sites.This work represents a breakthrough in the development of high-efficient non-precious-metal catalysts(NPMCs)to address the current Pt-based electrocatalysts challenges.
文摘开展6 000和10 000 k N·m能级强夯的现场试验,以强夯前后多道瞬态面波测试和重型动力触探试验方法,对强夯处理效果进行测试。试验结果表明:强夯加固处理后地基承载力和土体工程特性得到改善,但地基承载力特征值和压缩模量局部深度仍不能满足设计要求;6 000和10 000 k N·m能级有效加固深度分别为6.0~7.0 m和7.0~8.0 m;10 000 k N·m能级试验区浅层加固处理效果较差,与浅层存在淤泥质土、夯坑回填方式及第3遍夯点间距过大和夯能过小等因素有关,需采取相应的处理措施。
