Methanol to hydrogen conversion on cobalt–ceria catalysts prepared by magnetron sputtering

Methanol oxidation catalyzed by bi-layered or mixed oxides of cobalt and cerium was studied at atmospheric pressure by temperature-programmed reaction technique. The catalysts were deposited in the form of thin films by magnetron sputtering from Co and CeO2 targets, forming double layer structures of CeO2/CoOx or CoOx/CeO2. Reaction selectivity and hydrogen production rates were monitored at O2:CH3OH reactant stoichiometries varied in the range 4:1–1:4, spanning from oxygen rich to oxygen lean reaction conditions. A complementary information in regard to thermal stability of the catalytic layers was obtained by X-ray photoelectron spectroscopy. A strong synergistic interaction between cerium and cobalt within the mixed oxide (driving dynamics of the Co2+/Co3+ and Ce4+/Ce3+ redox pairs and oxygen exchange) leads to a bi-functional catalyst. Particularly the CeO2/CoOx configuration proved to be significantly more active than the CoOx alone and more stable, especially under reducing environments. Further optimization of reactivity can be provided via control of the adlayer coverage.