Universal Principles for the Rational Design of Single Atom Electrocatalysts? Handle with Care

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 (SACs) and, in particular, of 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 with a rapidly growing number of theoretical studies based on density functional theory (DFT) and with proposals of universal descriptors that should provide a guide to the experimentalist for the synthesis of efficient catalysts. In this Perspective we critically analyze some of the current problems connected with the prediction of the activity of SACs: accuracy of the calculations, neglect of important contributions in the models used, physical meaning of the proposed descriptors, not to mention some problems of reproducibility. It follows that the "rational design" of a catalyst based on some of the proposed universal descriptors should be considered with caution.