Ionic Liquid-Modified Electrocatalysts: The Interaction of [C₁C₂Im][OTf] with Pt(1 1 1) and its Influence on Methanol Oxidation Studied by Electrochemical IR Spectroscopy

详细信息    查看全文

• 作者：Olaf Brummel^a ; ^{olaf.brummel@fau.de" class="auth_mail" title="E-mail the corresponding author} ; Firas Faisal^a ; ^{afiras.faisal@fau.de" class="auth_mail" title="E-mail the corresponding author} ; Tanja Bauer^a ; ^{tanja.bauer@fau.de" class="auth_mail" title="E-mail the corresponding author} ; Kaija Pohako-Esko^b ; ^{kaija.pohaka-esko@fau.de" class="auth_mail" title="E-mail the corresponding author} ; Peter Wasserscheid^b ; ^c ; ^{wasserscheid@crt.cbi.uni-erlangen.de" class="auth_mail" title="E-mail the corresponding author} ; Jö ; rg Libuda^a ; ^c ; ^{joerg.libuda@fau.de" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Ionic liquids ; platinum ; electrochemical IR spectroscopy ; methanol oxidation ; carbon monoxide
• 刊名：Electrochimica Acta
• 出版年：2016
• 出版时间：10 January 2016
• 年：2016
• 卷：188
• 期：Complete
• 页码：825-836
• 全文大小：4336 K

文摘

Ionic liquids (ILs) have recently been proposed as modifying agents to tune the selectivity and the activity of electrocatalysts. In order to explore the origin of IL-induced effects on electrocatalytic reactions, we have investigated (i) the interaction of [C₁C₂Im][OTf]–water mixtures with Pt(1 1 1) single crystal electrodes and (ii) the influence of [C₁C₂Im][OTf] on methanol oxidation in acidic aqueous solution using cyclic voltammetry (CV) and electrochemical IR spectroscopy.

We show that [C₁C₂Im][OTf] interacts strongly with the Pt(1 1 1) surface in the potential range from -0.2 V_Ag/AgCl to 0.65 V_Ag/AgCl, leading to partial blocking of the surface, partial suppression of hydrogen adsorption, and partial suppression of OH_ads formation. The interaction of the IL with Pt occurs in this potential range via specific adsorption of the [OTf]⁻ anions which bind to Pt(1 1 1) via the SO₃⁻ group in a tilted adsorption geometry. The adsorption process is largely reversible as a function of the electrode potential, but shows a complex kinetics and becomes very slow at high IL coverage. Also, [C₁C₂Im][OTf] has a strong effect on the electro-oxidation of methanol in acidic solution. Adsorption of [OTf]⁻ leads to partial blocking of the indirect oxidation pathway to CO. The onset potential for CO oxidation is found to be shifted to more positive values indicating hindered access of H₂O to the electrode surface. CO and the [C₁C₂Im][OTf] form a mixed co-adsorption layer which is characterized by a strongly red-shifted CO stretching band. The effect is assigned to an IL-induced ligand effect in the mixed adsorbate layer and suggests that the direct modification of active centers by surface-bound IL species plays an important role in IL-modified electrocatalytic materials.