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Kinetics Study on O2 Adsorption and OHad Desorption at Pt(111), Its Implication to Oxygen Reduction Reaction Kinetics (cited: 1)
Fan Yang,Ling-wen Liao,Ming-fang Li,Dong Mei,Yan-xia Chen*
Author NameAffiliationE-mail
Fan Yang Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China  
Ling-wen Liao Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China  
Ming-fang Li Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China  
Dong Mei Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China  
Yan-xia Chen* Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China yachen@ustc.edu.cn 
Abstract:
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/cm2 at 0.8 V, the fast kinetics of OHad desorption indicates that it should not be the rate determining step for ORR. In the kinetic- or 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.
Key words:  Oxygen reduction reaction, Pt(111) electrode, Rate determining step, Kinetics, Overpotential, Thermodynamic equilibrium
FundProject:
Pt(111)电极上O2与OHad的吸脱附及氧还原反应动力学 (cited: 1)
杨帆,廖玲文,李明芳,梅东,陈艳霞*
摘要:
研究了Pt(111)电极在0.1 mol/L HClO4溶液中O2吸附与OHad脱附及氧还原反应的动力学.研究发现OHad的可逆吸脱附速率很快;在氧还原的动力学或动力学与传质混合控制区,恒电位下氧还原的电流随反应时间缓慢衰减,在转速较大,扫速较慢的情形下正向扫描过程中氧还原的电流总是明显低于逆向扫描的电流;Pt/0.1 mol/L HClO4从无O2切换到O2
关键词:  氧还原反应,Pt(111)电极,反应决速步,动力学,热力学平衡,超电势
DOI:10.1063/1674-0068/27/04/479-484
分类号: