Carbon Dioxide Electroreduction at Highly Porous Nitrogen and Sulfur Co-Doped Iron-Containing Heterogeneous Carbon Gel

The functionalized carbon nanostructure, nitrogen and sulfur co-doped iron-containing highly porous carbon gel (obtained via carbonization of corresponding organic gel) is considered here as a non-precious metal catalyst for the electroreduction of carbon dioxide in neutral solution (potassium bicarbonate at pH = 6.8). Various electrochemical measurements (performed in distinct modes and under different conditions) have been utilized to comment about the catalyst performance and the reaction mechanism, in particular about the reaction products and the relative contribution from hydrogen evolution. At low overpotentials, the carbon dioxide reduction is favored over the hydrogen evolution reaction. Combination of conventional (stationary) stripping-type and hydrodynamic (rotating ring-disk electrode) voltammetric approaches has been demonstrated to function as an unique electroanalytical tool here. The CO2-reduction products can be identified as adsorbates (oxidative stripping voltammetry) or monitored continuously (electrooxidation) at the Pt ring electrode. Finally, the results of both electrochemical diagnostic and parallel gas chromatographic analytical measurements are consistent with the view that, in the examined range of the potentials, CO is the main CO2-reduction product.