Electrocatalytic reduction of CO2 to CO over iron phthalocyanine-modified graphene nanocomposites

Abstract

The non-precious materials with iron-pyrrolic nitrogen-carbon (Fe–N–C) moiety have attracted an increasing attention on the CO2 reduction reaction (CO2RR). However, the influence of iron valence state and environmental synergy is not still clear. Here, iron phthalocyanine (FePc) molecule with an intrinsic Fe–N4–C moiety is enough dispersed on graphene as the single-atom iron catalyst through a facile chemical method. The FePc-graphene composites with different FePc content and iron valence state are synthesized to investigate their catalysis for the CO2RR to CO. The onset overpotential of 190 mV and Faradaic efficiency of >90% may be achieved in the optimal composites. Experimental and calculational results prove the positive role and synergy of Fe(II)Pc with Fe(III)Pc and graphene. The formation of ∗COOH intermediate is confirmed to be the rate-limiting step. The theoretical calculation reveals that Fe(II)Pc should have higher activity than Fe(III)Pc, and Fe(II)Pc/FePc(III) dimer may be better than individual one. This work clearly exhibits the effect of Fe2+/3+- pyrrolic N4–C on the CO2RR.