Enhancing CO2 Conversion to CO over Plasma-Deposited Composites Based on Mixed Co and Fe Oxides

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

doi:10.3390/catal11080883

Hanna Kierzkowska-Pawlak, Klaudia Łyszczarz + Show 7 more

Open Access

https://doi.org/10.3390/catal11080883

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Abstract

The hydrogenation of CO2 to produce CO and H2O, known as reverse-water-gas shift reaction (RWGS) is considered to be an important CO2 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 CO2 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 CH4, while the Fe-based catalyst, containing crystalline Fe2O3/Fe3O4 phases, was less active and converted CO2 mainly into CO. Regarding the Fe–Co nanocomposites (incl. Fe2O3/Fe3O4 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 CO2, 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 p–n junctions between nanoparticles of cobalt and iron oxides.

Highlights

The capture of CO2 from large industrial sources followed by storage (CCS) or use (CCU) is considered an efficient way of mitigating tons of emitted CO2
The activity of the new Fe–Co composites was evaluated in the CO2 hydrogenation in the temperature range of 250–400 ◦ C
Plasma-prepared nanocomposites give several thin-film catalysts deposited on a wiremesh support with different ratios of iron to cobalt

Summary

Introduction

The capture of CO2 from large industrial sources followed by storage (CCS) or use (CCU) is considered an efficient way of mitigating tons of emitted CO2. The CCU approach involves the use of CO2 and co-reactants to create new products [1]. There are different paths of CO2 transformation into synthetic fuels and valuable chemicals by means of biological or chemical processes. Using “renewable” hydrogen obtained from carbon-free energy sources, new products of commercial interest can be obtained. Using this approach, CO2 should be no longer considered to be a pollutant but an attractive carbon source acting as a feedstock for the subsequent synthesis [3,4]

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