Quantum chemical studies of transition metal single-atom catalysts: exploration of catalytic descriptors

Abstract

Spin states of transition metal (TM) based catalysts play important roles in their catalytic performances. However, the lack of investigation on their intrinsic structure–property relationship greatly limits the rational control of spin states. Herein, we present a systemic first-principles study of O₂ activation, CO oxidation, H₂O dissociation, and CO₂ dissociation on TM (Fe, Co, and Ni) single-atom catalysts (SACs) with different spin states. The calculation results indicate that the spin population can be changed by reactant adsorption in the catalytic processes. Through rational manipulation of the TM type and spin, the activity of TM-SAC can be significantly improved. To shed light on the enhancement mechanism and explore some universal descriptors for TM-SACs, a series of structure–property relationships were systemically surveyed. It was found that the interactions between TM and O are very crucial for the binding stability/reactivity of the oxygen-containing reactants. Accordingly, the parameters that can reflect TM and O interactions, including TM–O bond length, key-species (O₂), spin moment, and charge transfer (charge on reactant), are all good descriptors for the catalytic performances of different models. More intriguingly, novel spectral descriptors, such as the stretching vibrational frequency of TM–O/O–O/O–H, were also found to have a good linear relationship with the reactivity.