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 FeN 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.