Electrochemical in-situ activation of Fe-oxide nanowires for the reverse water gas shift reaction

Abstract

The catalytic activity of FeOx nanowires (Ø = 5−6 nm) deposited on yttria-stabilized zirconia (YSZ) solid-electrolyte was enhanced through the application of external current or potential for the reverse water gas shift (RWGS) reaction. As shown by XPS, the as-prepared FeOx nanowires consist of the mixture of oxides: Fe2O3, Fe3O4 and some FeO. The nanowires showed 99 % selectivity to CO under both open-circuit and electrochemical polarization. We found that the oxidation state of iron depended on the reaction temperature and was in-situ controlled and modified upon anodic and cathodic polarization. Anodic polarization at 335 and 400 °C led to a 200 % increase in the reaction rate due to the electrooxidation of inactive FexC and supply of oxygen ions from YSZ to FeOx resulting in the formation of active oxide. Cathodic polarization resulted in up to 4-fold rate increase due to catalyst reduction increasing the coverage of CO2 on the surface.