Electrocatalysis by Single-Atoms—A Modeling Perspective

One of the objectives of electronic structure theory is to predict chemical and catalytic activities. This is a challenging target due to the large number of variables that determine the performance of a heterogeneous catalyst. The complexity of the problem has reduced considerably with the advent of single atom catalysts (SAC), new systems consisting of a single transition metal stabilized on a solid matrix. SACs offer great potential advantages compared to more conventional supported metal nanoparticles in terms of selectivity and of material needs in order to prepare the catalysts. A lot of attention has been given in particular to graphene-based SACs for electrocatalytic reactions such as the oxygen reduction (ORR), the oxygen evolution (OER) and the hydrogen evolution (HER) reactions. In this context we assist to a rapidly growing number of theoretical studies based on density functional theory (DFT) and of proposals of universal descriptors that should provide a guide to the experimentalist for the synthesis of new catalysts. In this talk we critically analyze some of the current problems connected with the prediction of the activity of SACs based on DFT: accuracy of the calculations, neglect of important contributions in the models used, physical meaning of the proposed descriptors, inaccurate data sets used to train machine learning algorithms, not to mention some severe problems of reproducibility. It follows that the “rational design” of a catalyst based on some of the proposed universal descriptors or of the DFT screening of large number of structures should be considered with great caution [1-3].<br/><br/>[1] G. Di Liberto, Luis A. Cipriano, G. Pacchioni, “Role of Dihydride and Dihydrogen Complexes in Hydrogen Evolution Reaction on Single-Atom Catalysts”, J. of the American Chemical Society, 143, 20431−20441 (2021).<br/>[2] G. Di Liberto, Luis A. Cipriano, G. Pacchioni, “Universal principles for the rational design of single atom electrocatalysts? Handle with care”, ACS Catalysis, 12, 5846-5856 (2022).<br/>[3] G. Di Liberto, S. Tosoni, L. Cipriano, G. Pacchioni, "A Few Questions about Single Atom Catalysts: When Modeling Helps", Accounts of Materials Research, 3, 986-995 (2022).