Fernández José L, Bard Allen J
Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712, USA.
Anal Chem. 2003 Jul 1;75(13):2967-74. doi: 10.1021/ac0340354.
The oxygen reduction reaction (ORR) in acidic medium was studied on different electrode materials by scanning electrochemical microscopy (SECM) operating in a new variation of the tip generation-substrate collection mode. An ultramicroelectrode tip placed close to the substrate electrode oxidizes water to oxygen at a constant current. The substrate is held at a potential where the tip-generated oxygen is reduced and the resulting substrate current is measured. By changing the substrate potential, it is possible to obtain a polarization (current-potential) curve, which depends on the electrocatalytic activity of the substrate material. The main difference between this mode and the classical feedback SECM mode of operation is that the feedback diffusion process is not required for the measurement, allowing its application for studying the ORR in acidic solutions. Activity-sensitive images of heterogeneous surfaces, e.g., with Pt and Au electrodes, were obtained from the substrate current when the x-y plane was scanned with the tip. The usefulness of this technique for imaging electrocatalytic activity of smooth metallic electrodes and of highly dispersed fuel cell-type electrocatalysts was demonstrated. The application of this method to the combinatorial chemical analysis of electrode materials and electrocatalysts is discussed.
采用扫描电化学显微镜（SECM）在尖端产生-基底收集模式的一种新变体下，研究了酸性介质中的氧还原反应（ORR），所用的电极材料各不相同。置于靠近基底电极的超微电极尖端以恒定电流将水氧化为氧气。基底保持在一个电位，在此电位下尖端产生的氧气被还原，并测量由此产生的基底电流。通过改变基底电位，可以获得一条极化（电流-电位）曲线，该曲线取决于基底材料的电催化活性。此模式与经典的反馈SECM操作模式的主要区别在于，测量不需要反馈扩散过程，这使得它可用于研究酸性溶液中的ORR。当用尖端扫描x-y平面时，从基底电流获得了异质表面（例如带有Pt和Au电极）的活性敏感图像。证明了该技术对于成像光滑金属电极和高度分散的燃料电池型电催化剂的电催化活性的有用性。讨论了该方法在电极材料和电催化剂的组合化学分析中的应用。
