Metal-Coordination Effects on the Stability and ORR/OER Activity of Layered Organometallic Single-Atom Catalysts: A Theoretical Study
Pedro H. Souza, Victor Hoyos-Sinchi, Walter Orellana
Abstract
Organometallic layered materials have emerged as promising single-atom catalysts for oxygen reduction and evolution reactions, but their practical use has been limited by insufficient electrochemical stability. Here, we present a density functional theory study clarifying the relationship between catalytic activity and stability in organometallic single-atom catalysts with metal-N4 (MN4) and metal-O4 (MO4) coordination. We compare graphene-embedded MN4 motif and phthalocyanine-like frameworks with MO4-coordination frameworks, including M4(OHPTP)2 and M3(HHTP)2 (M = Mn, Fe, Co, Ni, Cu, Zn). Stability is assessed by surface Pourbaix analysis, while activity is evaluated using the computational hydrogen electrode method. MN4 systems show competitive overpotentials but suffer strong pH-dependent instability. In contrast, MO4 frameworks exhibit enhanced robustness across wide pH ranges while maintaining good catalytic performance. A proposed stability descriptor enables direct comparison across systems, identifying MO4 coordination structures, particularly M4(OHPTP)2 (M = Zn, Co) as optimal for balancing activity and stability in practical electrocatalysis.