Detail:

Abstract:
　　In situ scanning tunneling microscopy (STM) is considered as the most direct means to probe the static structures and dynamic reaction at electrified interfaces. This technique has been used to study the conformation of conducting polymers of aniline and pyrrole, effect of organic additive on electrodeposition of copper, the electrocatalysis of artificial metal adlayer. Some results in these three research topics are discussed below. All results are obtained with single crystal electrodes, as they afford a well-defined and ordered substrate on which atoms or molecules are adsorbed. Electrochemical potentials mentioned below are against reversible hydrogen electrode (RHE)
　　Although platinum (Pt) is active toward a wide range of reactions, including hydrogen evolution and oxidation, oxygen reduction, methanol oxidation etc., its high cost has been the notorious factor to its applications. One of the direct strategies to counteract this is to reduce Pt loading in the electrodes. Platinum (Pt) monolayer deposited on ordered Au(111) substrate is chosen as a model system to understand the structure and property of supported Pt monolayer. We devise a simple method to fabricate a Pt overlayer on Au(111) electrode, where PtCl62− complexes are reduced to metallic Pt atoms by CO molecules without potential control. The adsorption of CO molecules first mobilized and rearranged Pt adatoms on Au(111) from disordered Pt aggregates to 0.9 nm wide tortuous stripes, and then to patches of ordered atomic arrays at 0.1 V.
　　Polyaniline (PAN) and polypyrrole (Ppy) are the most famous conducting organics. The control of the molecular structures and film morphology are crucial to their future development. STM imaging provides a direct view of these polymers as they are electrochemically deposited on Au(111) electrode in nitric, sulfuric, perchloric, and hydrochloric acids. As the potential was modulated between 0.8 and 0.6 V, the conformation of PAN molecules changed from linear to crooked (Figure 2a and b). This potential - driven change in molecular conformations was fast and reversible in nitric acid and perchloric acids, but was largely irreversible in sulfuric acid. This contrast resulted from unlike interaction strength between anions in these acidic electrolytes and PAN molecules. Figure 2c-e show in situ STM images collected with polypyrrole deposited on Au(111) electrode by two potential cycling between 0.05 and 0.9 V in 0.1 H2SO4 + 30 mM pyrrole. The brightness of oligo- or polypyrrole molecules in the STM images directly reflects their heights on the gold electrode. These STM images provide direct views of oxidized polypyrrole molecules, which are conformed to accommodate the charges at the electrode. STM images provide a direct view of polypyrrole molecules which have been difficult to be tracked until now.