Co-adsorption of Fluoride and Hydroxide Ions on Ag(111) in Alkaline Electrolytes: Electrochemical and SHG Studies
Co-adsorption of Fluoride and Hydroxide Ions on Ag(111) in Alkaline Electrolytes: Electrochemical and SHG Studies
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碱性电解质中氟化物和氢氧根离子在 Ag(111) 上的共吸附：电化学和二次谐波研究
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
K. Doblhofer
中科院分区：
文献类型：
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作者：
M. Danckwerts;E. Savinova;S. Horswell;B. Pettinger;K. Doblhofer
摘要Ag（111）/碱性电解质界面上的氢氧化物（OH−）吸附是导致表面氧化物形成的第一步。我们研究了OH−阴离子吸附如何受到支持电解质阴离子（F−）共吸附的影响。研究了纯NaF和NaOH以及pH=5.8 ~ 14的混合电解质。测量二次谐波产生（SHG）信号的旋转各向异性，以区分吸附过程从Ag表面上的结构变化。我们的研究结果清楚地表明，从F-为主的OH-为主的吸附交叉，而这两个物种在吸附时保持带电。在更正的电势下，但低于本体氧化物生长的可逆电势，OH被放电，导致亚单层氧化物积聚，而在酸性电解质中，Ag被溶解。在中等pH值下，提出了结构化OH−/F−共吸附层的形成。
Abstract Hydroxide (OH−) adsorption at Ag(111)/alkaline electrolyte interfaces is the initial step leading to the formation of surface oxide. We investigate how OH− anion adsorption is influenced by co-adsorption of supporting electrolyte anions (F−). Pure NaF and NaOH as well as mixed electrolytes ranging from pH=5.8 to 14 are investigated. The rotational anisotropy of the second harmonic generation (SHG) signal is measured to distinguish adsorptive processes from structural changes on the Ag surface. Our results clearly show a cross-over from F−-dominated to OH−-dominated adsorption, while both species remain charged upon adsorption. At more positive potentials, but below the reversible potential of bulk oxide growth, OH is discharged leading to sub-monolayer oxide build-up, whereas in acidic electrolyte, Ag is dissolved. At intermediate pH, the formation of a structured OH−/F− co-adsorbed layer is proposed.