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

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 dz2 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.