The Activity of Oxygen Reduction Reaction on the Noble Metal Doped Titanium Oxide in Acidic Electrolyte

摘要

Titanium oxide with the oxygen vacancies is expected as one of the candidates for the non-platinum catalyst of polymer electrolyte fuel cells. The reasons why the activity of titanium oxide improves by the presence of oxygen vacancies are assumed the formation of the active site and the micro electron-conducting path. From the viewpoint of enhancement of the electron conductivity, it is well known that doping a transition metal to titanium oxide is also effectiveness method. Thus, many papers had reported about the niobium doped titanium oxide to increase the electron conductivity. However, not only the doping transition metals but also the oxygen vacancies are necessary to obtain high activity of the titanium oxide. We put forward a possibility that the crystal distortion acts as the active site. Now, we think that the majority role of transition metal doping is the formation of the micro electro-conducting path to the active site. Hence, we were attending to the electron conductivity of transition metal-doped titanium oxide. From the results of a theoretical calculation, the electron conductivity of niobium doped titanium oxide, which is researched well as the non-platinum catalyst, is relatively low. And, ruthenium and iridium as doping species give high electron conductivity to titanium oxide. Ruthenium and iridium are famous for interacting with titanium oxide in the electrolysis field. In this study, the activity of oxygen reduction reaction (ORR) of ruthenium or iridium doped titanium oxide was evaluated.