Electrocatalytic Activity of Hydrazine in Fqel Cell Applications

The electrode reactions of hydrazine in acid and basic solutions on smooth and platinised platinum have "been examined. From analysis of the rest potentials and concentration relationships a rapid one electron exchange with a stable surface species has "been postulated. The mechanism of oxidation occurs via a sequential system whereby hydrazinium radicals are the products of the initial oxidation. The electrode reactions of carbon monoxide in acid solutions on smooth platinum electrodes have also been examined. The carbon monoxide is strongly bound to the metal surface and probably exists as a compound, Suppression of the reversible hydrogen reaction was observed in the presence of CO. Removal of the carbon monoxide film was performed as soon as oxide formation occurred indicating that the carbon monoxide is essentially electro-inactive and that the reaction is purely chemical with the metal oxide to form carbon dioxide. Electrochemical regeneration of the metal oxide forms the regenerative cycle. MO + 00-^ M + C02 M + H2O ->. MO + 2H + 2e-. The oxidation of methanol in acid does not proceed via carbon monoxide as en intermediate. ^AUV —■ »— '——^gmmmm Electrode Reactions of Hydrazine As a potential fuel for fuel cell studies, hydrazine Is convenient as it is soluble in the electrolyte and stähle, thus eliminating the problems of triple phase studies using porous electrodes. Preliminary work on the electro-oxidation has indicated that the reaction is rapid over the total four electron steps, i.e., N^a5 + -«*> N2 + 5H + + he' 0) Although several workers have examined this system in both acid and alkaline media, there is considerable disagreement between authors. 1 Pavela, working in alkaline media on platinum and gold, concluded that the .iuxtaposition of the reversible hydrogen potential was the moat significant factor and that the hydrogen atoms were stripped from the hydrazine molecule and subsequently oxidized, giving an over-all mechanism of a low pressure 2 hydrogen electrode. Recently, Baker and Eisenberg came to the same conclusion as Pavela, indicating that the hydrogen discharge was rate controlling. 5 In conflict with this view were the works of Meites and Kazp k and of Bard where the effect of the surface state of platinum electrode was investigated and consideration was made for an intermediate redox system using the platinum oxide (or hydroxide) to facilitate the reaction. e.g., 2(Pt + Hj£ —> PtO+ 2H*" + ae") 1 . SPtO + H^5 —> aPt + Na + 2H5P + H" J 5 ^ Finally, Susbielles and Bloch considered the presence of two concurrent reactions, one befng the oxidation of hydra^lue while the other was the reaction of the electrolyte. \ e.g., NsJU + kOR—► Ha + ^H^O + W I (5) 2H^0 + 2e" —> 20H" + Ha |