Multiple C–C bond formation upon electrocatalytic reduction of CO₂ by an iron-based molecular macrocycle

Abstract

Molecular macrocycles are very promising electrocatalysts for the reduction of carbon dioxide into value-added chemicals. Up to now, most of these catalysts produced only C1 products. We report here that...

Mechanism of CO2 Electroreduction to Multicarbon Products over Iron Phthalocyanine Single-Atom Catalysts

“…The low activation energies for more reduced complexes, on the other hand, indicate that H 2 is produced over PcFe("0") and PcFe("-I"). Therefore, H 2 is, in line with experimental evidence, 16 likely to be formed at applied potentials lower than −0.7 V.…”

“…Therefore, more negative potentials shift the selectivity from CO toward post-CO products, which is observed experimentally. 16 PcFe−COH formation is unlikely due to the very low potential of almost −2.10 V independent of the formal oxidation state (see Supporting Information). The hydrogenation of PcFe−CO to form PcFe−CHO has a potential of approximately 0 V for all oxidation states (Figure 4; right arrow).…”

“…This is, however, contrary to the experiment, which indicates that, irrespective of the applied potential, always the amount of CO is significantly higher than that of post-CO products. 16 Thus, the activation energy cannot solely explain the observed selectivity. Indeed, the proton supply is highly limited by the very low concentration of H 3 O + at pH = 7 ([H + ] = 10 −7 ).…”

“…However, our previous study 16 surprisingly demonstrated that C 2+ products can also be formed over single-atom molecular catalysts like iron phthalocyanine (PcFe) albeit with a very low faradaic efficiency, while these systems are wellknown to only produce C1 products. 17,18 Based on the abovementioned study, 16 PcFe is capable of producing light hydrocarbons such as C 2 H 4 and C 3 H 6 through the electrocatalytic CO 2 reduction in aqueous solutions under neutral pH conditions. Based on their experimental evaluations, we suggested that CO is an essential reactant in the pathways of CO 2 reduction to C 2+ .…”

Multiscale effects in tandem CO2 electrolysis to C2+ products

“…Furthermore, recent examples of C 2+ products stemming from molecular catalysts opens routes to tune multicarbon selectivity through ligand and metal modifications. 84 Aside from CO-based tandem pathways common to Cu catalysts, other metals have recently demonstrated C 2 -C 4 production in cascade pathways stemming from formate-pathway intermediates rather than those that generate CO, and could therefore be utilised in tandem catalysis based on alternative primary products. [85][86][87] When comparing multi-cell with single-cell tandems, there are a number of different considerations.…”