Low-temperature hydrogen reduction of pure Co 3O 4 and doped with palladium

Abstract

Kinetic studies of the hydrogen interaction with pure or palladium-doped Co 3O 4 under 0.01–0.07 KPa pressure at 195–320 K revealed a first-order reaction. For Co 3O 4 the rate constant decreases more than two orders while the activation energy increases twice, after 10% of an oxygen monolayer is reacted. Ultimate reduction of Co 3O 4 is 1.5 wt%. For Pd: Co 3O 4 under the same conditions, the rate constant increases twice and the activation energy decreases four times. Ultimate reduction was found to be 20 wt%. XPS measurements at room temperature revealed higher activity of Pd: Co 3O 4 for reduction. Hydrogen reacting with Pd: Co 3O 4 at room temperature partially reduces Co 2+ to Co metal, increases the content of OH - or O - ions (BE 531.2 eV) and produces an electron-rich oxygen form (528.3 eV) unstable under a vacuum heating. Palladium was present in a heavy-reduced state [Pd-PdO] red. The mechanism of the reaction is discussed.