Single-Atom Catalysts: Are You Really Single?

Single-atom catalysts (SACs) have attracted the attention of the scientific community due to a number of attractive properties allowing their application in different catalytic processes, including electrochemical ones. Due to the nature of the active site, consisting of only a few atoms, SACs are also very attractive for theoretical modeling as the active site can be directly translated into the computational model. However, as a rule, the possibility of the active site change induced by pH and electrode potential is disregarded in theoretical models. This Perspective emphasizes the need to address the actual state of SA electrocatalysts under operating conditions before considering their catalytic activity and selectivity. The concept of surface Pourbaix plot, well-known in electrochemistry, can be directly transferred to SACs, providing valuable insights and guidance for developing novel catalytic materials. We discuss recent approaches to designing Pourbaix plots for SACs and outline the importance of properly treating the actual state of SACs and other emerging types of catalysts.