Catalysis in Liquid Water: From Metalloporphyrins to Graphene M–N4 Single-Atom Sites

Organometallic complexes provide a suitable framework to analyze the interplay between electronic structure, spin state, and catalytic activity. In this talk, we will focus on metalloporphyrins and phthalocyanines as model systems for the oxygen reduction reaction (ORR), discussing the role of the metal center identity and the influence of catalyst preparation methods (UHV vs solution). In the second part, we will present recent ongoing research on Metal–N4 active sites embedded in graphene under in operando conditions,in line with studies of single-atom catalysts in liquid water (Fe, Co, and Ni). We will show how the spin state influences the adsorption of water molecules and the local structure of the aqueous environment. To address this, we combine machine-learning-based interatomic potentials (MACE) with ab initio molecular dynamics simulations. This part of the work is a collaboration with Romain Reocreux and Marie-Laure Bocque (ENS, Paris).