Ir has long been regarded as an alternative ethanol-to-CO electrocatalyst, but little is known about the ethanol oxidation reaction (EOR) mechanism on Ir, especially the C1 pathway selectivity. Thereby, in situ quasi-quantitative electrochemical infrared absorption spectroscopy (QEIAS), consisting of total-reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), infrared absorption spectroscopy (IRAS), and transmission infrared absorption spectroscopy (TIAS) with a thin-layer flow cell, is established to probe it. Initially, the well-accepted EOR dual-pathway mechanism is confirmed via ATR-SEIRAS and IRAS. Ir-H species (ca. 2040 cm), originating from the ethanol dissociation at low potentials, are observed for the first time to replenish the reaction process. Based on it, the apparent Faradaic efficiency of the C1 pathway () is readily estimated to be as high as 76.4% (0.7 V) in acidic media. The quantitative analysis of reaction residual verifies these results through high-performance liquid chromatography (HPLC), and a relative error of only 2–9% exists between the two methods. Thus, Ir might be more efficient for ethanol complete oxidation than other Pt-group metallic catalysts, especially in acidic media. This work could be necessary for the rational design of Ir-based EOR catalysts with high C1 pathway selectivity and low over-potential for direct ethanol fuel cells.

中文翻译：

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Ir 电极上电催化乙醇对 CO2 的选择性：准定量电化学红外吸收光谱研究

长期以来，Ir 一直被认为是一种替代乙醇制 CO 的电催化剂，但人们对 Ir 的乙醇氧化反应 (EOR) 机制，尤其是 C1 途径选择性知之甚少。因此，原位准定量电化学红外吸收光谱（QEIAS）由全反射表面增强红外吸收光谱（ATR-SEIRAS）、红外吸收光谱（IRAS）和透射红外吸收光谱（TIAS）组成，具有薄层建立层流动池来探测它。最初，广为接受的 EOR 双途径机制是通过 ATR-SEIRAS 和 IRAS 得到证实的。首次观察到源自低电位乙醇解离的 Ir-H 物种（约 2040 cm）以补充反应过程。基于此，在酸性介质中，C1 途径 () 的表观法拉第效率很容易估计高达 76.4% (0.7 V)。反应残留的定量分析通过高效液相色谱（HPLC）验证了这些结果，两种方法之间的相对误差仅为2%~9%。因此，对于乙醇完全氧化，Ir 可能比其他 Pt 族金属催化剂更有效，尤其是在酸性介质中。这项工作对于合理设计具有高 C1 路径选择性和低过电势的直接乙醇燃料电池 Ir 基 EOR 催化剂可能是必要的。