Center for Electrochemistry and Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712, USA.
J Am Chem Soc. 2009 Dec 2;131(47):17046-7. doi: 10.1021/ja907626t.
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(-) and CO(2) 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) approximately = 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 CO(2) 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 H(2)SO(4) through which CO was bubbled gave a precipitate of BaCO(3) 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.
扫描电化学显微镜表面询问（SI-SECM）在循环伏安模式下成功地用于通过与电生成的 Br(2)反应检测和定量吸附在 Pt 电极上的 CO。该新技术中使用的两电极设置允许在询问器尖端上产生 Br(2)，当开路时，这在 Pt 基底上方报告瞬态正反馈，表明该卤素与 CO((ads))的反应性。Br(-)和 CO(2)被证明是反应的主要产物（在没有 O(2)的情况下），这可能涉及溴代光气作为可水解中间体的形成。在饱和条件下，在多晶 Pt 表面上可重现地定量 CO((ads))，theta(CO)约为 0.5。反应被预吸附氰化物的作用阻断，这证明了该过程的表面性质。在一个体相实验中进一步测试了 CO(2)作为最终产物的形成：将 Pt 黑添加到含有 Br(2)的 0.5 M H(2)SO(4)混合物中，通过该混合物中鼓泡 CO，在 Ba(OH)(2)的饱和溶液中得到 BaCO(3)的沉淀物。使用 SI-SECM 允许访问通过单个电极上的常规电化学难以证明的反应。
