Fullerene Promotes CO2 Reduction to Methanol by a Cobalt(II) Phthalocyanine Electrocatalyst

Abstract

Heterogenization of molecular electrocatalysts offers an attractive way to improve the catalytic selectivity and efficiency of CO₂ conversion to liquid fuels. Herein, we employ density functional theory to compare the mechanism of CO₂RR by a cobalt(II) tetra(amino)phthalocyanine (Co(II)Pc(NH₂)₄) electrocatalyst with and without the presence of fullerene support. Our DFT calculations suggest that the CO₂ reduction mechanism is initiated by a metal-based electron reduction followed by subsequent CO₂ nucleophilic addition, electron transfer, proton transfer, water dissociation, and proton-coupled electron transfer steps that lead to CO and methanol formation. We show that graphitic interactions between the Co(II)Pc(NH₂)₄ electrocatalyst and C₆₀ support selectively improve the CO₂RR to methanol at mild potentials. The undesirable hydrogen evolution reaction (HER) was also investigated for both electrocatalysts and proceeds via the protonation of the cobalt metal center over the nitrogen atom in the inner ring. The competition between the HER and the CO₂RR was improved in favor of CO and methanol formation using the Co(II)Pc(NH₂)₄@C₆₀ electrocatalyst. Overall, our results suggest C₆₀ as a promising graphitic support for molecular electrocatalysts integration for CO₂ catalysis.