Pt-Ni alloy nanocrystals with Pt-enriched shells were prepared by selective etching of surface Ni using sulfuric acid and hydroquinone.The changes in the electronic and geometric structure of the alloy nanoparticles a...Pt-Ni alloy nanocrystals with Pt-enriched shells were prepared by selective etching of surface Ni using sulfuric acid and hydroquinone.The changes in the electronic and geometric structure of the alloy nanoparticles at the surface were elucidated from the electrochemical surface area,the potential of zero total charge(PZTC),and relative surface roughness,which were determined from CO-and CO_(2)-displacement experiments before and after 3000 potential cycles under oxygen reduction reaction conditions.While the highest activity and durability were achieved in hydroquinone-treated Pt–Ni,sulfuric acidtreated one showed the lower activity and durability despite its higher surface Pt concentration and alloying level.Both PZTC and QCO_(2)/QCO ratio(desorption charge of reductively adsorbed CO_(2) normalized by COad-stripping charge)depend on surface roughness.In particular,QCO_(2)/QCO ratio change better reflects the roughness on an atomic scale,and PZTC is also affected by the electronic modification of Pt atoms in surface layers.In this study,a comparative study is presented to find a relationship between surface structure and electrochemical properties,which reveals that surface roughness plays a critical role to improve the electrochemical performance of Pt-Ni alloy catalysts with Pt-rich surfaces.展开更多
The cathode of biofuel cell reduces molecular oxygen to water using four electrons, an enzyme of multicopper oxidase family, laccase, is contained, though its electron transfer efficiency from the electrode resulted i...The cathode of biofuel cell reduces molecular oxygen to water using four electrons, an enzyme of multicopper oxidase family, laccase, is contained, though its electron transfer efficiency from the electrode resulted in rate determining process. To improve this electron, transfer via mediators, we have investigated several mediator metal complexes between the electrode and laccase, in particular hydrophobic pocket on the surface. We have discussed DFT computational results and selected experimental data of new Mn(III/II) Schiff base complexes having redox active (anthraquinone) ligands and photochromic (azobenzene) ligands about azobenzene moiety at the sole molecular level. Moreover, we carried out computational docking simulation of laccase and complexes considering trans-cis photoisomerization (electronic states) and Weigert effect (molecular orientation to fit better) of azobenzene moiety. Additionally, actual experimental data also presented to indicate the expected merits for mediators.展开更多
Iron sulfides have bee n con sidered as one of the most promising can didates for sodium ion battery anode materials due to their high theoretical capacity and low cost. I n this work, spin dle-like Fe7S8 with n itrog...Iron sulfides have bee n con sidered as one of the most promising can didates for sodium ion battery anode materials due to their high theoretical capacity and low cost. I n this work, spin dle-like Fe7S8 with n itroge rvdoped carb on (FeiS/N-C) nano hybrids are successfully syn thesized via a solvothermal method by sulfidation iron-based metal organic framework (FeMOF). As sodium ion battery an odes, FeySs/N-C nano hybrids exhibit high reversible capacity of 450.8 mAh g-1 at 200 mA·g^-1, and 406.7 mAh·g^-1 at 500 mA·g^-1 even after 500 cycles. They also show excellent rate properties and delivering the capacity of 327.8 mAh·g^-1 at a very high current density of 3.2 A·g^-1. These outstanding electrochemical performa nces can be attributed to the unique structure of Fe7S8/ N-C nan ohybrids. The nano scale dime nsion in their size can be ben eficial for facile ion and electro n tran sports. Furthermore, the stable n itroge n doped carb on frameworks can also improve electrical conductivity and relieve the problems related to volume expansion. X-ray absorption spectroscopy and X-ray photoelectron spectroscopy analyses have been performed to study reactions occurred in spindle-like FeySs/N-C nanohybrid electrode at both bulk and surface.展开更多
High energy ball-milled iron sulfides with thin carb on layer coati ng(BM-FeS/C composites)were prepared by the simple and econo mical process.Ball-milled process,followed by carb on coati ng,reduced the particle size...High energy ball-milled iron sulfides with thin carb on layer coati ng(BM-FeS/C composites)were prepared by the simple and econo mical process.Ball-milled process,followed by carb on coati ng,reduced the particle size and increased the electrical con ductivity.Whe n employed as sodium-ion battery ano des,BM?F eS/C composites showed extremely high electrochemical performa nee with reversible specific capacity of 589.8 mAh·g^-1 after 100 cycles at a current density of 100 mA·g^-1.They also exhibited superior rate capabilities of 375.9 mAh·g^-1 even at 3.2 Ag^1 and 423.6 mAh·g^-1 at 1.5 Ag_1.X-ray absorptio n near edge structure an alysis con firmed the electrochemical pathway for con version reaction of BM-FeS/C composites.展开更多
基金This study was supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.2019R1F1A1062193).
文摘Pt-Ni alloy nanocrystals with Pt-enriched shells were prepared by selective etching of surface Ni using sulfuric acid and hydroquinone.The changes in the electronic and geometric structure of the alloy nanoparticles at the surface were elucidated from the electrochemical surface area,the potential of zero total charge(PZTC),and relative surface roughness,which were determined from CO-and CO_(2)-displacement experiments before and after 3000 potential cycles under oxygen reduction reaction conditions.While the highest activity and durability were achieved in hydroquinone-treated Pt–Ni,sulfuric acidtreated one showed the lower activity and durability despite its higher surface Pt concentration and alloying level.Both PZTC and QCO_(2)/QCO ratio(desorption charge of reductively adsorbed CO_(2) normalized by COad-stripping charge)depend on surface roughness.In particular,QCO_(2)/QCO ratio change better reflects the roughness on an atomic scale,and PZTC is also affected by the electronic modification of Pt atoms in surface layers.In this study,a comparative study is presented to find a relationship between surface structure and electrochemical properties,which reveals that surface roughness plays a critical role to improve the electrochemical performance of Pt-Ni alloy catalysts with Pt-rich surfaces.
文摘The cathode of biofuel cell reduces molecular oxygen to water using four electrons, an enzyme of multicopper oxidase family, laccase, is contained, though its electron transfer efficiency from the electrode resulted in rate determining process. To improve this electron, transfer via mediators, we have investigated several mediator metal complexes between the electrode and laccase, in particular hydrophobic pocket on the surface. We have discussed DFT computational results and selected experimental data of new Mn(III/II) Schiff base complexes having redox active (anthraquinone) ligands and photochromic (azobenzene) ligands about azobenzene moiety at the sole molecular level. Moreover, we carried out computational docking simulation of laccase and complexes considering trans-cis photoisomerization (electronic states) and Weigert effect (molecular orientation to fit better) of azobenzene moiety. Additionally, actual experimental data also presented to indicate the expected merits for mediators.
文摘Iron sulfides have bee n con sidered as one of the most promising can didates for sodium ion battery anode materials due to their high theoretical capacity and low cost. I n this work, spin dle-like Fe7S8 with n itroge rvdoped carb on (FeiS/N-C) nano hybrids are successfully syn thesized via a solvothermal method by sulfidation iron-based metal organic framework (FeMOF). As sodium ion battery an odes, FeySs/N-C nano hybrids exhibit high reversible capacity of 450.8 mAh g-1 at 200 mA·g^-1, and 406.7 mAh·g^-1 at 500 mA·g^-1 even after 500 cycles. They also show excellent rate properties and delivering the capacity of 327.8 mAh·g^-1 at a very high current density of 3.2 A·g^-1. These outstanding electrochemical performa nces can be attributed to the unique structure of Fe7S8/ N-C nan ohybrids. The nano scale dime nsion in their size can be ben eficial for facile ion and electro n tran sports. Furthermore, the stable n itroge n doped carb on frameworks can also improve electrical conductivity and relieve the problems related to volume expansion. X-ray absorption spectroscopy and X-ray photoelectron spectroscopy analyses have been performed to study reactions occurred in spindle-like FeySs/N-C nanohybrid electrode at both bulk and surface.
文摘High energy ball-milled iron sulfides with thin carb on layer coati ng(BM-FeS/C composites)were prepared by the simple and econo mical process.Ball-milled process,followed by carb on coati ng,reduced the particle size and increased the electrical con ductivity.Whe n employed as sodium-ion battery ano des,BM?F eS/C composites showed extremely high electrochemical performa nee with reversible specific capacity of 589.8 mAh·g^-1 after 100 cycles at a current density of 100 mA·g^-1.They also exhibited superior rate capabilities of 375.9 mAh·g^-1 even at 3.2 Ag^1 and 423.6 mAh·g^-1 at 1.5 Ag_1.X-ray absorptio n near edge structure an alysis con firmed the electrochemical pathway for con version reaction of BM-FeS/C composites.
