Combined surface analytical and electrochemical investigations of RuTiSn mixed oxide electrocatalysts

Abstract

Using a galvanostatic oxygen exposure, it can be shown by XPS and SEEM that admixtures of Sn (2 at. yo) to RTO anodes inhibit the corrosion of both the bulk ruthenium species and the titanium substrate interface. The inhibitor effect is strongly dependent on the Sn segregation t o the surface region blocking the channels of oxygen diffusion in incoherent active layers for C1, evolution.Mit Hilfe einer galvanostatischen Sauerstoffbelastung von RTO Anodon fur die Erzeugung von C1, wird in Kombination mit XPS und SEM gezeigt, daB eine Zugabe von 2 at. % Sn sowohl die Korrosion der Ruthenium-Spezies im Volumen und damit auch die der Titansubstrat-Grenzschicht verhindert. Der Inhibitor-Effekt entsteht durch eine SnSegregation in den oberflachennahen Bereich, wodurch die Diffusionskaniile fur Sauerstoff in der inkoharenten Aktivschioht blockiert werden.

Effect of Composition on the Electrocatalytic Activity of the Ternary Oxide Ru0.3Ti ( 0.7 − x ) Sn x O 2 : I . Oxygen Evolution from Solutions

“…Reasons for that are unknown. It might be due to a defect of preparation, or to a specific action of SnO2 in the presence of TiO2 (6). It is intriguing that Eo~ differs systematically by ca.…”

“…However, that effect is to be attributed to the combined action of Pd and Sn, since our results would predict a poorer selectivity. Selective dissolution of Ru with respect to Sn has been determined by x-ray fluorescence (10), and this effect has been invoked to explain the observed decrease in electrocatalytic activity after extensive 02 evolution (6). Surface segregation of Sn has been suggested to explain why the rate of 02 evolution is depressed as SnO2 replaces TiO2 in small amounts (11).…”

“…This new system is unique in that it allows release of macromolecules and proteins (e.g., insulin) (6). This composite membrane electrorelease system consists of a microporous support membrane which is covered with a nonporous barrier layer (6). When the barrier layer is intact, the reagent to be released is entrapped in the microporous membrane.…”

“…Another reason is that the presence of SnO2 is claimed to enhance selectivity in the process of chlorine production (3,4). A third reason is that SnO2 has been observed to improve the lohg-term stability of DSA electrodes (5,6). However, if SnO~ is doped with Sb, it already shows surprisingly good electrocatalytic properties (7).…”

“…Besides Ref. (3) and (5), they include: a voltammetric study of a single composition [20 + 68 + 12 mole percent (m/o)] (8), for which a correlation between the electrocatalytic activity for chlorine evolution and the catalyst loading has also been reported (9); an analytical application of energy-dispersive x-ray fluorescence as a non-destructive technique to monitor the surface composition of DSA (10); a surface analysis by x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) of(Ru + Ti)O2 containing up to 2 m/o SnO2 (6); and a structural investigation over a wide composition range by means of x-ray diffraction and conductivity measurements (11). Corollary papers are those dealing with Ru-doped SnO2 electrodes (12)(13)(14)(15).…”