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Atomically dispersed Fe3+ sites catalyze efficient CO2 electroreduction to CO

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Science  14 Jun 2019:
Vol. 364, Issue 6445, pp. 1091-1094
DOI: 10.1126/science.aaw7515

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Three's a charm for iron and CO2

Large-scale electrochemical reduction of CO2 to CO could be a promising first step in sustainable conversion of the greenhouse gas to commodity chemicals. Currently, gold and silver are the most active catalysts for this process, whereas more abundant, less expensive metals tend to require impractically high potentials. Jun Gu et al. now report an iron catalyst with activity equaling or exceeding that of the precious metals. The key proved to be stabilization of the dispersed single iron ions in the +3 oxidation state.

Science, this issue p. 1091

Abstract

Currently, the most active electrocatalysts for the conversion of CO2 to CO are gold-based nanomaterials, whereas non–precious metal catalysts have shown low to modest activity. Here, we report a catalyst of dispersed single-atom iron sites that produces CO at an overpotential as low as 80 millivolts. Partial current density reaches 94 milliamperes per square centimeter at an overpotential of 340 millivolts. Operando x-ray absorption spectroscopy revealed the active sites to be discrete Fe3+ ions, coordinated to pyrrolic nitrogen (N) atoms of the N-doped carbon support, that maintain their +3 oxidation state during electrocatalysis, probably through electronic coupling to the conductive carbon support. Electrochemical data suggest that the Fe3+ sites derive their superior activity from faster CO2 adsorption and weaker CO absorption than that of conventional Fe2+ sites.

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