Enhancing CO<sub>2</sub> Conversion to CO over Plasma-Deposited Composites Based on Mixed Co and Fe Oxides

oleh: Hanna Kierzkowska-Pawlak, Małgorzata Ryba, Maciej Fronczak, Ryszard Kapica, Jan Sielski, Maciej Sitarz, Patryk Zając, Klaudia Łyszczarz, Jacek Tyczkowski

Format: Article
Diterbitkan: MDPI AG 2021-07-01

Deskripsi

The hydrogenation of CO<sub>2</sub> to produce CO and H<sub>2</sub>O, known as reverse-water-gas shift reaction (RWGS) is considered to be an important CO<sub>2</sub> valorization pathway. This work is aimed at proposing the thin-film catalysts based on iron and cobalt oxides for this purpose. A series of Fe–Co nanocomposites were prepared by the plasma-enhanced chemical vapor deposition (PECVD) from organic cobalt and iron precursors on a wire-mesh support. The catalysts were characterized by SEM/EDX, XPS, XRD, and Raman spectroscopy and studied for hydrogenation of CO<sub>2</sub> in a tubular reactor operating in the temperature range of 250–400 °C and atmospheric pressure. The Co-based catalyst, containing crystalline CoO phase, exhibited high activity toward CH<sub>4</sub>, while the Fe<sub>-</sub>based catalyst, containing crystalline Fe<sub>2</sub>O<sub>3</sub>/Fe<sub>3</sub>O<sub>4</sub> phases, was less active and converted CO<sub>2</sub> mainly into CO. Regarding the Fe–Co nanocomposites (incl. Fe<sub>2</sub>O<sub>3</sub>/Fe<sub>3</sub>O<sub>4</sub> and CoO), even a small fraction of iron dramatically inhibited the production of methane. With increasing the atomic fraction of iron in the Fe–Co systems, the efficiency of the RWGS reaction at 400 °C increased up to 95% selectivity to CO and 30% conversion of CO<sub>2</sub>, which significantly exceeded the conversion for pure iron–based films (approx. 9%). The superior performance of the Fe–Co nanocomposites compared to “pure” Co and Fe–based films was proposed to be explained by assuming changes in the electronic structure of the catalyst resulting from the formation of <i>p</i>–<i>n</i> junctions between nanoparticles of cobalt and iron oxides.