Advances in plasma produced CoOx-based nanocatalysts for CO2 methanation

Abstract

Series of CoOX and CoOX/TiO2 nanocatalysts for the conversion of CO2 to methane were produced in the form of thin films supported on wire gauze using the plasma-enhanced chemical vapor deposition (PECVD) from volatile cobalt and titanium organic complexes. The results show that conditions of the plasma deposition process and the subsequent thermal treatment in air or argon atmosphere determine the structure and the catalytic performance of the resulting thin films. Investigations of the surface chemical structure of the catalytic films, performed by X-ray photoelectron spectroscopy (XPS), revealed the presence of cobalt in different oxidation states: Co+3, Co+2, Co°, the content of which depends on the processing path. Interestingly, not metallic cobalt but its oxidation states were found to be active in the CO2 methanation. Among the different CoOx-based films, the specific structure of CoO in graphite-like matrix obtained after calcination in argon, revealed superior performance over the CoOx and CoOX/TiO2 films calcined in air. At 400 °C, it achieved a high CO2 conversion and selectivity to methane of 73% and 94%, respectively (GHSV = 1500 cm3 h−1 gcat−1). Moreover, there was no deactivation for the CoO in graphite-like matrix during time-on-stream at 400 °C indicating an excellent stability.