Mechanistic understanding of 3d-metal phthalocyanine catalysts: heterostructure regulation of dz2 orbitals for efficient CO2 reduction

Abstract

Heterostructure molecular catalysts have attracted significant attention for their distinctive catalytic activity in the electrocatalytic CO₂ reduction reaction. To investigate the intrinsic reaction mechanisms, 3d-transition metal-phthalocyanine-based catalysts were systematically investigated. The results demonstrate that the heterostructure catalysts, composed of 3d-transition metal phthalocyanine and two-dimensional nitrogen-doped graphene, successfully modulate the electron configuration of the central metal atom and push its d_z² orbitals close to the Fermi level which can lower the energy barrier for the rate-limiting step in its electrocatalytic CO₂ reduction reaction (CRR) and boost the overall reaction kinetics. In addition, the mechanism of dual-site synergistic hydrogenation was determined for the first time through molecular dynamics simulation. Meanwhile, the descriptors related to metal atoms' inherent characteristics and catalytic properties exhibit a volcano relationship with the overpotential. This study provides a theoretical comprehension of the CRR mechanisms over heterostructure molecular catalysts, as well as innovative concepts for new molecular catalyst design.