A balanced detection of both adsorbates and dissolved species is very important for the clarification of the electrochemical reaction mechanism yet remains a major challenge for different modes of electrochemical infrared (IR) spectroscopy. Among others, conventional attenuated total reflection-surface-enhanced IR absorption spectroscopy (ATR-SEIRAS) is far less sensitive to low-concentration solution species than to surface species. We report herein an electrochemical wide-frequency ATR-SEIRAS with a novel thin-layer flow cell design, fulfilling the simultaneous detection of the variations of surface and solution species. This setup consists of a silicon wafer (with one side micromachined and the other side metallized), a thin-layer electrolyte structure with tunable thickness and flow rate, and a tilt-correction system based on laser collimation, enabling a well-controlled mass transport within the electrolyte layer and the spectral differentiation of solution species from adsorbates. Using acidic methanol oxidation on a Pt film electrode as a model system, besides SEIRA bands for adsorbed CO and formate intermediates, IR spectral signals for dissolved products CO₂, formic acid, and methyl formate can be readily identified for a quiescent electrolyte layer of ∼20 μm, which are otherwise undetected with conventional ATR-SEIRAS, as indicated by the trend of spectral features with increasing thickness or flow rate.

中文翻译：

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用于同时检测电化学中吸附和溶解物质的电解质层可调 ATR-SEIRAS

吸附物和溶解物质的平衡检测对于阐明电化学反应机制非常重要，但对于不同模式的电化学红外 (IR) 光谱仍然是一个主要挑战。其中，传统的衰减全反射表面增强红外吸收光谱 (ATR-SEIRAS) 对低浓度溶液物质的敏感性远低于对表面物质的敏感性。我们在此报告了一种具有新型薄层流通池设计的电化学宽频 ATR-SEIRAS，可同时检测表面和溶液种类的变化。该装置由硅晶片（一侧微加工，另一侧金属化）、厚度和流速可调的薄层电解质结构以及基于激光准直的倾斜校正系统组成，能够在电解质层内实现良好控制的质量传输以及溶液物质与吸附物的光谱区分。使用 Pt 膜电极上的酸性甲醇氧化作为模型系统，除了吸附 CO 和甲酸盐中间体的 SEIRA 波段，溶解产物 CO 的 IR 光谱信号_如图2所示，甲酸和甲酸甲酯可以很容易地识别出约 20 μm 的静态电解质层，而传统的 ATR-SEIRAS 则无法检测到，如光谱特征随厚度或流速增加的趋势所示。