Reaction of Br2 with Adsorbed CO on Pt, Studied by the Surface Interrogation Mode of Scanning Electrochemical Microscopy
Reaction of Br2 with Adsorbed CO on Pt, Studied by the Surface Interrogation Mode of Scanning Electrochemical Microscopy
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DOI：
10.1021/ja907626t
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发表时间：
2009-12-02
影响因子：
15
通讯作者：
Bard, Allen J.
中科院分区：
文献类型：
--
作者：
Wang, Qian;Rodriguez-Lopez, Joaquin;Bard, Allen J.
利用循环伏安模式下的扫描电化学显微镜（SI-SECM），通过电生成的Br-2对Pt电极上吸附的CO进行了检测和定量。在这种新技术中使用的双电极设置允许在询问器尖端上生产Br-2，该探针在开路时报告了Pt衬底上方的瞬态正反馈，作为该卤素与CO（ads）的反应性的指示。Br-2和CO2被证明是反应的主要产物（在没有O-2的情况下），这可能涉及形成溴光气作为可水解的中间体。在饱和条件下，CO（ads）可在多晶Pt表面重现定量，θ (CO)近似于0.5。该反应被预吸附氰化物的作用所阻断，这表明了该工艺的表面特征。在散装实验中进一步测试了作为最终产物的CO2的形成：在0.5 M H2SO4中向Br-2混合物中加入Pt黑，使CO起泡，在Ba(OH)(2)的饱和溶液中产生BaCO3的沉淀。使用SI-SECM可以获得难以通过传统电化学在单个电极上证明的反应。
Scanning electrochemical microscopy surface interrogation (SI-SECM) in the cyclic voltammetry mode was successfully used to detect and quantify adsorbed CO on a Pt electrode by reaction with electrogenerated Br-2. The two-electrode setup used in this new technique allowed the production of Br-2 on an interrogator tip, which reported a transient positive feedback above a Pt substrate at open circuit as an indication of the reactivity of this halogen with CO(ads). Br-2 and CO2 are shown to be the main products of the reaction (in the absence of O-2), which may involve the formation of bromophosgene as a hydrolyzable intermediate. Under saturation conditions, CO(ads) was reproducibly quantified at the polycrystalline Pt surface with theta(co) approximate to 0.5. The reaction is shown to be blocked by the action of pre-adsorbed cyanide, which demonstrates the surface character of the process. The formation of CO2 as an end product was further tested in a bulk experiment: addition of Pt black to a mixture of Br-2 in 0.5 M H2SO4 through which CO was bubbled gave a precipitate of BaCO3 in a saturated solution of Ba(OH)(2). The use of SI-SECM allowed access to a reaction that would otherwise be difficult to prove through conventional electrochemistry on a single electrode.