Despite substantial efforts in developing high-performance catalysts for the oxygen reduction reaction(ORR),the persistent challenge lies in the high onset overpotential of the ORR,and the effect of the elec-trolyte s...Despite substantial efforts in developing high-performance catalysts for the oxygen reduction reaction(ORR),the persistent challenge lies in the high onset overpotential of the ORR,and the effect of the elec-trolyte solution cannot be ignored.Consequently,we have systematically investigated the impact of adsorbate species and concentration,as well as solution pH,on the ORR activity on Pt(111)and Pt(poly)electrodes.The results all tend to establish a linear quantitative relationship between the onset potential for ORR and the adsorption equilibrium potential of the adsorbate.This finding indicates the decisive role of adsorbates in the onset potential for ORR,suggesting that the adsorption potential of adsorbates can serve as an intuitive criterion for ORR activity.Additional support for this conclusion is derived from experimental results obtained from the oxygen evolution reaction on Pt(poly)with different adsorbate species and from the hydrogen evolution reaction on Pt(111)with iodine adsorption.We further propose both an empirical equation for the onset potential for ORR and the concept of a potential-regulated adsor-bate shielding effect to elucidate the influence of adsorbates on ORR activity.This study provides new insights into the high onset overpotential of the ORR and offers potential strategies for predicting and enhancingORRactivity inthefuture.展开更多
A detailed study of the cyclic voltammtry curve of Pt(111) electrode in H2SO4 solution by X-ray photoe1ectron spectroscopy (XPS) and a low energy electron diffeaction (LEED) has provided firstly direct evidence that t...A detailed study of the cyclic voltammtry curve of Pt(111) electrode in H2SO4 solution by X-ray photoe1ectron spectroscopy (XPS) and a low energy electron diffeaction (LEED) has provided firstly direct evidence that the anomalous features reported originally by Clavilier et al. are associated with the specific adsorption of sulfate ainons rather than hydrogen adsorption. The ()R30 structure on Pt(111) obtained after electrode emersion on the positive scan at more positive potentials than 0.23V vs. Ag/AgCl appears sedtaneously with sharp increase of XPS of O1s and S2p. This implies the relationship between anomalous peak and sulfate anion adsorption on emersed Pt(111 ) electrode.展开更多
利用单晶旋转圆盘电极技术(Hanging Meniscus Rotating Disk Electrode,HMRD)在硫酸和高氯酸溶液中,分别研究了甘氨酸修饰的Pt(111)电极表面氧分子的电催化还原反应.实验发现:在硫酸溶液中,经甘氨酸修饰的Pt(111)电极表面的氧还原活性...利用单晶旋转圆盘电极技术(Hanging Meniscus Rotating Disk Electrode,HMRD)在硫酸和高氯酸溶液中,分别研究了甘氨酸修饰的Pt(111)电极表面氧分子的电催化还原反应.实验发现:在硫酸溶液中,经甘氨酸修饰的Pt(111)电极表面的氧还原活性明显提高,其中氧还原的半波电位与Pt(111)电极的相比正移约0.1 V,而在高氯酸溶液中,甘氨酸修饰的Pt(111)电极的活性几乎没有发生变化.该实验结果表明:甘氨酸修饰的Pt(111)电极一方面抑制了SO42-在电极表面的吸附,另一方面又能在电极表面提供相邻的空位供氧分子吸附.通过与文献中报道的CN-修饰的Pt(111)电极上的氧还原结果的对比,可以推测甘氨酸修饰的Pt(111)电极表面氧还原活性提高,是由于甘氨酸在Pt(111)表面可能先被氧化成CN-后吸附在电极表面,进而促进了氧分子的电催化还原反应.展开更多
Kinetics of dissociative O2 adsorption, OHad desorption, and oxygen reduction reaction （ORR） at Pt（111） electrode in 0.1 mol/L HClO4 has been investigated. Reversible OHad adsorption/desorption occurs at potential...Kinetics of dissociative O2 adsorption, OHad desorption, and oxygen reduction reaction （ORR） at Pt（111） electrode in 0.1 mol/L HClO4 has been investigated. Reversible OHad adsorption/desorption occurs at potentials from 0.6 V to 1.0 V （vs. RHE） with the exchange current density of ca. 50 mA/cm^2 at 0.8 V, the fast kinetics of OHad desorption indicates that it should not be the rate determining step for ORR. In the kineticor kinetic-mass transport mix controlled potential region, ORR current at constant potential displays slight decrease with reaction time. ORR current in the positive-going potential scan is slightly larger than that in the subsequent negative-going scan with electrode rotation speed （〉800 r/min） and slow potential scan rate （〈100 mV/s）. The open circuit potential of Pt/0.1 mol/L HClO4 interface increases promptly from 0.9 V to 1.0 V after switch from O2 free- to O2-saturated solution. The increase of open circuit potential as well as ORR current decays under potential control due to the accumulation of OHad from dissociative adsorption of O2. It indicates that at Pt（111） the net rate for O2 decomposition to OHad is slightly faster than that for OHad removal, one cannot simply use the assumption of rate determining step to discuss ORR kinetics. Instead, the ORR kinetics is determined by both the kinetics for O2 decomposition to OHad as well as the thermo-equilibrium of OHad＋H^＋＋e→←H2O.展开更多
Fast scan voltammetry is an efficient tool to distinguish oxidative/reductive adsorp- tion/desorption from that for bulk reaction. In this work, we provide a methodology that the isotherm of oxidative/reductive adsorp...Fast scan voltammetry is an efficient tool to distinguish oxidative/reductive adsorp- tion/desorption from that for bulk reaction. In this work, we provide a methodology that the isotherm of oxidative/reductive adsorption desorption processes at electrode surface can be obtained using just one solution with relatively low reactant concentration, by taking the advantage of varying the potential scan rate （relative of the diffusion rate） to tune the adsorption rate and proper mathematic treatment. The methodology is demonstrated by taking acetate adsorption at Pt（lll） in acidic solution as an example. The possibility for extension of this method toward mechanistic studies of complicated electrocatalytic reactions is also given.展开更多
基金supported by the National Natural Science Foundation of China(no.22372154,21972131).
文摘Despite substantial efforts in developing high-performance catalysts for the oxygen reduction reaction(ORR),the persistent challenge lies in the high onset overpotential of the ORR,and the effect of the elec-trolyte solution cannot be ignored.Consequently,we have systematically investigated the impact of adsorbate species and concentration,as well as solution pH,on the ORR activity on Pt(111)and Pt(poly)electrodes.The results all tend to establish a linear quantitative relationship between the onset potential for ORR and the adsorption equilibrium potential of the adsorbate.This finding indicates the decisive role of adsorbates in the onset potential for ORR,suggesting that the adsorption potential of adsorbates can serve as an intuitive criterion for ORR activity.Additional support for this conclusion is derived from experimental results obtained from the oxygen evolution reaction on Pt(poly)with different adsorbate species and from the hydrogen evolution reaction on Pt(111)with iodine adsorption.We further propose both an empirical equation for the onset potential for ORR and the concept of a potential-regulated adsor-bate shielding effect to elucidate the influence of adsorbates on ORR activity.This study provides new insights into the high onset overpotential of the ORR and offers potential strategies for predicting and enhancingORRactivity inthefuture.
文摘A detailed study of the cyclic voltammtry curve of Pt(111) electrode in H2SO4 solution by X-ray photoe1ectron spectroscopy (XPS) and a low energy electron diffeaction (LEED) has provided firstly direct evidence that the anomalous features reported originally by Clavilier et al. are associated with the specific adsorption of sulfate ainons rather than hydrogen adsorption. The ()R30 structure on Pt(111) obtained after electrode emersion on the positive scan at more positive potentials than 0.23V vs. Ag/AgCl appears sedtaneously with sharp increase of XPS of O1s and S2p. This implies the relationship between anomalous peak and sulfate anion adsorption on emersed Pt(111 ) electrode.
基金supported by the National Natural Science Foundation of China(21503122,21346002)Natural Science Foundation of Shanxi for Youths,China(2014021016-2)+1 种基金Scientific and Technological Programs in Shanxi Province,China(2015031017)Foundation of Key Laboratory of Advanced Energy Materials Chemistry(Ministry of Education),China~~
基金V. ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.20773116）, the National Instrumentation Program （No.2011YQ03012416）, and 973 Program from the Ministry of Science and Technology of China （No.2010CB923302）.
文摘Kinetics of dissociative O2 adsorption, OHad desorption, and oxygen reduction reaction （ORR） at Pt（111） electrode in 0.1 mol/L HClO4 has been investigated. Reversible OHad adsorption/desorption occurs at potentials from 0.6 V to 1.0 V （vs. RHE） with the exchange current density of ca. 50 mA/cm^2 at 0.8 V, the fast kinetics of OHad desorption indicates that it should not be the rate determining step for ORR. In the kineticor kinetic-mass transport mix controlled potential region, ORR current at constant potential displays slight decrease with reaction time. ORR current in the positive-going potential scan is slightly larger than that in the subsequent negative-going scan with electrode rotation speed （〉800 r/min） and slow potential scan rate （〈100 mV/s）. The open circuit potential of Pt/0.1 mol/L HClO4 interface increases promptly from 0.9 V to 1.0 V after switch from O2 free- to O2-saturated solution. The increase of open circuit potential as well as ORR current decays under potential control due to the accumulation of OHad from dissociative adsorption of O2. It indicates that at Pt（111） the net rate for O2 decomposition to OHad is slightly faster than that for OHad removal, one cannot simply use the assumption of rate determining step to discuss ORR kinetics. Instead, the ORR kinetics is determined by both the kinetics for O2 decomposition to OHad as well as the thermo-equilibrium of OHad＋H^＋＋e→←H2O.
基金This work was supported by one Hundred Talents＇ Program of the Chinese Academy of Science, the National Natural Science Foundation of China （No.20773116, No.21273215, and No.J1030412）, and 973 Program from theMinistry of Science and Technology of China （No.2010CB923302）. Many Thanks to Prof. Shen Ye from Hokkaido university for the help in establishing techniques for single crystalline electro- chemistry.
文摘Fast scan voltammetry is an efficient tool to distinguish oxidative/reductive adsorp- tion/desorption from that for bulk reaction. In this work, we provide a methodology that the isotherm of oxidative/reductive adsorption desorption processes at electrode surface can be obtained using just one solution with relatively low reactant concentration, by taking the advantage of varying the potential scan rate （relative of the diffusion rate） to tune the adsorption rate and proper mathematic treatment. The methodology is demonstrated by taking acetate adsorption at Pt（lll） in acidic solution as an example. The possibility for extension of this method toward mechanistic studies of complicated electrocatalytic reactions is also given.
