Unveiling the Neighboring Screening Effect and Strong p-d Coupling in CO2 Reduction on Graphene-Supported Metal-Free and Iron Phthalocyanine

Abstract

Phthalocyanine and its metal complex, with the support of graphene as the single atomic catalysts (SACs), have gained significant attention in electroreduction applications. However, the contributions from the neighbor atoms of the reaction site and the graphene support in CO₂ reduction reaction (CO₂RR) are not clear due to the complex reaction pathways involved. To explore the catalytic potential in CO₂RR, a theoretical study on phthalocyanine (H₂Pc) and iron phthalocyanine (FePc) is conducted to reveal detailed influences of adsorbing sites, reaction energy, and electron behaviors of the C₁ pathway. The screening shielding effect arising from the strong p-d coupling of the FeN binding is observed on the 2nd nearest neighboring site, thus, suppressing the neighboring effect. Meanwhile, two catalysts supported by graphene are fully investigated based on thermodynamic factors and the electron behaviors of graphene are interpreted. A higher CO₂RR activity facilitated by electrostatic repulsions of graphene is discovered on both catalysts. This work establishes a theoretical framework for metal phthalocyanine SACs integrated with graphene in CO₂RR catalysis and uncovers the trends of electron activities and catalytic performances.