NiOx-Pt/C nanocomposites: Highly active electrocatalysts for the electrochemical oxidation of hydrazine

Abstract

NiOx-modified Pt/C nanocomposites are synthesized and investigated for hydrazine electrooxidation in an alkaline electrolyte. The reaction onset potential is significantly reduced in comparison to that of pure Pt/C, owing to the occurrence of a bifunctional mechanism, in which OH species on Ni sites facilitate the oxidation of adsorbed H atoms on the Pt surface. On-line Differential Electrochemical Mass Spectrometry (DEMS) shows that NiOx-Pt/C catalyzes the heterogeneous chemical hydrolysis at open circuit potential, producing H2 and N2. Just above the OCP, the H2 signal in DEMS decreases concomitantly with the increase in faradaic current, due to quantitative H2 (and Had) electrooxidation on Pt, or due to the deceleration of the overall reaction of hydrolysis. At slightly higher potentials, the N2 signal further rises, which indicates the onset of complete electrooxidation of hydrazine. In the platinum-oxide region, the H2 signal increases again and this process is also accompanied by a small ionic signal of NH3, evidencing the occurrence of an incomplete hydrazine electrooxidation route, at least in a minor extent.