IN SITU Ru L_Ⅱ AND L_ Ⅲ EDGE X-RAY ABSORPTION NEAR EDGE STRUCTURE OF ELECTRODEPOSITED RUTHENIUM DIOXIDE FILMS

摘要

A detailed characterization of electronic and structural changes induced by changes in the applied potential of ruthenium dioxide is expected to provide much needed insight into the rather unique supercapacitive behavior this material displays in acid electrolytes. Analysis of in situ Ru K-edge extended X-ray absorption fine structure EXAFS(l) collected in our laboratory for electrodeposited RuO_2 films on Au was found to be consistent with a sizable decrease in the Ru-O bond distance from values characteristic of Ru(IV) for the material as prepared, to those of Ru(Ⅲ) compounds as the films were polarized negative to the broad voltammetric peak. Somewhat surprisingly, only very subtle differences were observed in the corresponding X-ray absorption near edge structure (XANES) region for Ru in the two oxidation states. As wilt be shown in this work, similar in situ XANES measurements at the Ru L_Ⅲ and L_Ⅱ edges revealed clearly discernable changes in both the positions and shapes of the white line, which support our early assignments.