Electrochemical Reduction of CO[sub 2] in the Micropores of Activated Carbon Fibers

CO 2 electroreduction was examined on high‐area metal (Fe, Ni, Cu, Pd) electrocatalysts supported on activated carbon fibers (ACF), which contain slit‐shaped pores with widths on the order of 2 nm. These catalysts exhibited relatively high selectivity ( ca. 67% total current efficiency for CO 2 reduction on ACF/Ni) and high partial current density (up to 63 mA cm − 2 for CO 2 reduction on ACF/Ni). Much smaller activities were observed for the same types of metal catalysts supported on nonactivated carbon fibers. The enhancement of the CO 2 reduction selectivity with the microporous support is thought to involve a nanospace effect, which gives rise to high‐pressure‐like effects at ambient pressure. The CO 2 reduction mechanism on Ni is proposed to involve an adsorbed CO 2 − CO 2 • − adduct, which is known to exist on the (110) surface.