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Effect of Sulfate Adlayer on Formic Acid Oxidation on Pd(111) Electrode
Jing Lei1, Zhen Wei1, Mian-le Xu1, Jie Wei1, Yan-xia Chen*1, Shen Ye2
1.Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China;2.Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, Japan
Abstract:
The kinetics of formic acid oxidation (FAO) on Pd(111) in 0.1 mol/L H2SO4+0.1 mol/LHCOOH with and without addition of Na2SO4 is studied using cyclic voltammetry and potential step method, which is compared with that in 0.1 mol/L HClO4. It is found that adsorbed sulfate has significant inhibition effect on FAO kinetics. After addition of 0.05 mol/L or 0.1 mol/L Na2SO4, FAO current in the negative-going scan is found to be significantly smaller than that at the same potential in the positive-going scan. We speculate that at potentials positive of the phase transition potential for the (SO4*ad)m+[(H2O)n-H3O+] or (SO4*ad)m+[Na+(H2O)n-H3O+] adlayer, the adlayer structure probably becomes denser and more stable with the increase of potential or with the addition of Na2SO4. The formation of connected adlayer network greatly enhance the stability of the adlayer, and the insertion of positive-charged H+ or Na+ into the adlayer network further reduces the electrostatic repulsion between partially charged sulfates. As a result, the destruction/desorption of compact sulfate adlayer becomes more difficult, which leaves much less free sites on the surface for FAO, and thus FAO kinetics at higher potentials and in the subsequent negative-going potential scan is significantly inhibited.
Key words:  Formic acid oxidation, Pd(111) electrode, Sulfate adsorption, Anions effect
FundProject:
硫酸(氢)根吸附层对Pd(111)电极上甲酸氧化反应的影响研究
雷 晶1, 韦 臻1, 许绵乐1, 魏 杰1, 陈艳霞*1, 叶 深2
1.中国科学技术大学化学物理系,合肥微尺度物质科学国家研究中心,合肥 230026;2.日本东北大学化学系,科学研究院,仙台
摘要:
本文使用循环伏安法和电势阶跃法分别研究了添加和不添加Na2SO4的0.1 mol/LH2SO4+0.1 mol/LHCOOH溶液中Pd(111)电极上甲酸氧化反应(FAO)的动力学行为,并与同样条件下0.1 mol/LHClO4中的动力学行为进行比较. 加入0.05 mol/L或者0.1 mol/LNa2O4后,在相同的电位下负向扫描的FAO电流比正向扫描的显著减小. 本文推测在(SO4*ad)m+[(H2O)n-H3O+]或(SO4*ad)m+[Na+(H2O)n-H3O+]吸附层相转变电势以正的电位, 这个吸附层的结构可能随着电位的增加或Na2SO4的加入变得更加致密和稳定. 因此,破坏或者脱附致密的硫酸(氢)根吸附层变得更加困难,使得FAO 动力学在较高电位和随后的负扫电位受到明显的抑制.
关键词:  甲酸氧化反应,Pd(111)电极,硫酸(氢)根吸附,阳离子效应
DOI:10.1063/1674-0068/cjcp1904079
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