The mechanical properties, thermodynamic features and their correlation were studied for La-Ce-Ni-Cu-Al high-entropy bulk metallic glasses （HE-BMGs）. Compressive testing indicated that the HE-BMGs are ductile on a m...The mechanical properties, thermodynamic features and their correlation were studied for La-Ce-Ni-Cu-Al high-entropy bulk metallic glasses （HE-BMGs）. Compressive testing indicated that the HE-BMGs are ductile on a microscopic scale but brittle on a macroscopic scale, because of the low fragility index rn of the HE-BMGs. In the non-isothermal process, the activation energies for glass transition for these HE-BMGs are the lowest of the known HE-BMGs. Large values of the Avrami exponent n imply that the crystallization process proceeded through three-dimensional growth and with an increasing nucleation rate. The activation energy for glass transition （Eg） is almost proportional to the HE-BMG fracture strength, because a higher Eg is required to dislodge the molecules from the glassy configuration for the HE-BMGs with a high strength. The findings provide unambiguous evidence for the correlation between the mechanical and thermodynamic properties.展开更多
Broadly,the oxygen evolution reaction(OER)has been deeply understood as a significant part of energy conversion and storage.Nevertheless,the anions in the OER catalysts have been neglected for various reasons such as ...Broadly,the oxygen evolution reaction(OER)has been deeply understood as a significant part of energy conversion and storage.Nevertheless,the anions in the OER catalysts have been neglected for various reasons such as inactive sites,dissolution,and oxidation,amongst others.Herein,we applied a model catalyst s-Ni(OH)2 to track the anionic behavior in the catalyst during the electrochemical process to fill this gap.The advanced operando synchrotron radiation Fourier transform infrared(SR-FTIR)spectroscopy,synchrotron radiation photoelectron spectroscopy(SRPES)depth detection and differential X-ray absorption fine structure(D-XAFS)spectrum jointly point out that some oxidized sulfur species(SO_(4)^(2-))will selfoptimize new Ni–S bonds during OER process.Such amazing anionic self-optimization(ASO)behavior has never been observed in the OER process.Subsequently,the optimization-derived component shows a significantly improved electrocatalytic performance(activity,stability,etc.)compared to reference catalyst Ni(OH)_(2).Theoretical calculation further suggests that the ASO process indeed derives a thermodynamically stable structure of the OER catalyst,and then gives its superb catalytic performance by optimizing the thermodynamic and kinetic processes in the OER,respectively.This work demonstrates the vital role of anions in the electrochemical process,which will open up new perspectives for understanding OER and provide some new ideas in related fields(especially catalysis and chemistry).展开更多
Numerous experiments have demonstrated that the metal atom is the active center of monoatomic catalysts for hydrogen evolution reaction(HER),while the active sites of nonmetal doped atoms are often neglected.By combin...Numerous experiments have demonstrated that the metal atom is the active center of monoatomic catalysts for hydrogen evolution reaction(HER),while the active sites of nonmetal doped atoms are often neglected.By combining theoretical prediction and experimental verification,we designed a unique ternary Ru-N_(4)-P coordination structure constructed by monodispersed Ru atoms supported on N,P dual-doped graphene for highly efficient hydrogen evolution in acid solution.The density functional theory calculations indicate that the charge polarization will lead to the most charge accumulation at P atoms,which results in a distinct nonmetallic P active sites with the moderate H∗adsorption energy.Notably,these P atoms mainly supply highly efficient catalytic sites with ultrasmall absorption energy of 0.007 eV.Correspondingly,the Ru-N_(4)-P demonstrated outstanding HER performance not only in an acidic condition but also in alkaline environment.Notably,the performance of Ru-NPC catalyst at high current is even superior to the commercial Pt/C catalysts,whether in acidic or alkaline medium.Our in situ synchrotron radiation infrared spectra demonstrate that a P-H_(ads) intermediate is continually emerging on the Ru-NPC catalyst,actively proving the nonmetallic P catalytically active site in HER that is very different with previously reported metallic sites.展开更多
文摘The mechanical properties, thermodynamic features and their correlation were studied for La-Ce-Ni-Cu-Al high-entropy bulk metallic glasses （HE-BMGs）. Compressive testing indicated that the HE-BMGs are ductile on a microscopic scale but brittle on a macroscopic scale, because of the low fragility index rn of the HE-BMGs. In the non-isothermal process, the activation energies for glass transition for these HE-BMGs are the lowest of the known HE-BMGs. Large values of the Avrami exponent n imply that the crystallization process proceeded through three-dimensional growth and with an increasing nucleation rate. The activation energy for glass transition （Eg） is almost proportional to the HE-BMG fracture strength, because a higher Eg is required to dislodge the molecules from the glassy configuration for the HE-BMGs with a high strength. The findings provide unambiguous evidence for the correlation between the mechanical and thermodynamic properties.
基金supported in part by the National Key R&D Program of China(2017YFA0303500)the National Natural Science Foundation of China(U1932201,21727801,and 51902303)+4 种基金the National Natural Science Foundation of China-Ministry of Foreign Affairs and International Cooperation of Italy(51861135202)CAS International Partnership Program(211134KYSB20190063)Key Research Program of Frontier Sciences(QYZDB-SSW-SLH018)the University of Science and Technology of China start-up fundCAS Interdisciplinary Innovation Team。
文摘Broadly,the oxygen evolution reaction(OER)has been deeply understood as a significant part of energy conversion and storage.Nevertheless,the anions in the OER catalysts have been neglected for various reasons such as inactive sites,dissolution,and oxidation,amongst others.Herein,we applied a model catalyst s-Ni(OH)2 to track the anionic behavior in the catalyst during the electrochemical process to fill this gap.The advanced operando synchrotron radiation Fourier transform infrared(SR-FTIR)spectroscopy,synchrotron radiation photoelectron spectroscopy(SRPES)depth detection and differential X-ray absorption fine structure(D-XAFS)spectrum jointly point out that some oxidized sulfur species(SO_(4)^(2-))will selfoptimize new Ni–S bonds during OER process.Such amazing anionic self-optimization(ASO)behavior has never been observed in the OER process.Subsequently,the optimization-derived component shows a significantly improved electrocatalytic performance(activity,stability,etc.)compared to reference catalyst Ni(OH)_(2).Theoretical calculation further suggests that the ASO process indeed derives a thermodynamically stable structure of the OER catalyst,and then gives its superb catalytic performance by optimizing the thermodynamic and kinetic processes in the OER,respectively.This work demonstrates the vital role of anions in the electrochemical process,which will open up new perspectives for understanding OER and provide some new ideas in related fields(especially catalysis and chemistry).
基金supported in part by the National Key R&D Program of China(2017YFA0303500),NSFC(U1932201,11574280,21727801,51902303,and 21978278)NSFCMAECI(51861135202)+2 种基金CAS Key Research Program of Frontier Sciences(QYZDB-SSW-SLH018)USTC start-up fund and CAS Interdisciplinary Innovation Team,and Fundamental Research Funds for the Central Universities(Grant No.WK2310000074)L.S.acknowledges the support from Key Laboratory of Advanced Energy Materials Chemistry(Ministry of Education),Nankai University(111 project,B12015).
文摘Numerous experiments have demonstrated that the metal atom is the active center of monoatomic catalysts for hydrogen evolution reaction(HER),while the active sites of nonmetal doped atoms are often neglected.By combining theoretical prediction and experimental verification,we designed a unique ternary Ru-N_(4)-P coordination structure constructed by monodispersed Ru atoms supported on N,P dual-doped graphene for highly efficient hydrogen evolution in acid solution.The density functional theory calculations indicate that the charge polarization will lead to the most charge accumulation at P atoms,which results in a distinct nonmetallic P active sites with the moderate H∗adsorption energy.Notably,these P atoms mainly supply highly efficient catalytic sites with ultrasmall absorption energy of 0.007 eV.Correspondingly,the Ru-N_(4)-P demonstrated outstanding HER performance not only in an acidic condition but also in alkaline environment.Notably,the performance of Ru-NPC catalyst at high current is even superior to the commercial Pt/C catalysts,whether in acidic or alkaline medium.Our in situ synchrotron radiation infrared spectra demonstrate that a P-H_(ads) intermediate is continually emerging on the Ru-NPC catalyst,actively proving the nonmetallic P catalytically active site in HER that is very different with previously reported metallic sites.
