In Part I hereof it was established that the rate of cathodic combustion of electrolytic gas is proportional to the current traversing the cathode zone. Subsequent investigations (III to IV) have shown that sputtered metal particles play an important rôle in the cathodic combustion of carbonic oxide, and that the nature of the cathode materials employed in the experiments described in (I) was therefore such as to render difficult a full interpretation of the results set forth therein; because, from the point of view of cathodic sputtering, copper occupies a position intermediate between the non-sputtering and freely sputtering classes of metals. Also, the results of recent experiments on the catalytic properties of sputtered platinum films, an account of which it is hoped will shortly be submitted to the Society, have shown that even at room temperature sputtered platinum is sometimes capable of powerfully catalysing the union of hydrogen and oxygen. These considerations clearly indicated the need for extending the study of the cathodic combustion of electrolytic gas to that occurring at electrodes such as gold, silver, tantalum and tungsten. Furthermore, with the object previously outlined in (VII),
i. e.
the elucidation of the mechanism of the combustion of hydrogen by oxygen and the rôle played by hydrogen in promoting the combustion of carbonic oxide, the scope of the present investigation was extended in order to study the effect of such diluents as oxygen, hydrogen and steam upon the cathodic combustion of electrolytic gas. The results of our experiments, of which an account is given in what follows, have shown,
inter alia
, that the rate of combustion of electrolytic gas at a non-sputtering cathode increases rapidly on dilution with hydrogen; whereas, at a freely sputtering cathode, this effect is far less pronounced.
Metal Exsolution to Enhance the Catalytic Activity of Electrodes in Solid Oxide Fuel Cells