Function of the support and metal loading on catalytic carbon dioxide reduction using ruthenium nanoparticles supported on carbon nanofibers

Abstract

Catalytic CO2 reduction has been performed using carbon nanofibers or nitrogen‐doped carbon nanofibers as a support for Ru nanoparticles. The catalyst that consists of 5 wt % Ru on nitrogen‐doped carbon nanofibers exhibited the highest conversion at a relatively low temperature, complete selectivity to CH4, and stable catalytic performance. The catalytic performance was substantially superior to catalysts supported on carbon nanotubes and akin to the best metal‐oxide‐supported catalyst in the literature. The characterization of the prepared catalyst by transient experiments (CO2 temperature‐programmed desorption, temperature‐programmed surface reaction, and transient response to CO2 removal) revealed that the catalyst support participates actively in the reaction. The Ru content governed the selectivity, which either favored CO formation for lower Ru contents (0.5–2 wt %) or CH4 formation for 5 wt % Ru loading. The mean Ru particle size determined by TEM was similar for each of the metal loadings. Therefore, the substantially different selectivity patterns cannot be attributed to structure sensitivity. The higher selectivity to CH4 can be explained by the enhanced supply of adsorbed hydrogen to the activated adsorbed CO intermediate, which was demonstrated to be the rate‐determining step.