Uncertainties in the reactivity of atomically dispersed catalytic metal: Can any single-atom catalyst work like a charm?

The exploration of atomically dispersed supported metal catalysts (ADSMCs) as a class of heterogeneous catalysts featuring ∼100% supported metal dispersion has greatly benefited from the intensive research on a subset of catalyst platforms named single-atom catalysts (SACs), in which isolated metal atoms are believed to be central to catalytic reactivity. Nevertheless, given the wide variety of ADSMC subfamilies, diverse metal-support synergy and interatomic interactions of the supported metal atoms should further enrich the design dome of SACs. Although most literature reports today focus on developing catalysts to host single-atom species with unique catalytic functions, there are far fewer, albeit significant, findings that clearly suggest uncertainties in the reactivities of single-atom species, where the fine-tuning of metal-support and interatomic interactions would cause reactivity shifts without altering the nominal catalyst formulation and ∼100% metal dispersion. This perspective discusses these uncertainties and their implications for future work.