Applications of Single-Atom Alloys in Thermal, Electro, and Photo Catalysis

Single-atom alloys (SAAs) are an emerging class of heterogeneous catalysts that maximize atom efficiency by embedding isolated reactive metal atoms within a host metal surface, creating well-defined active sites. Atomic isolation imparts unique catalytic properties, including high selectivity, resistance to poisoning, coking, and sintering, and in some cases the ability to circumvent conventional scaling relationships that limit traditional catalysts. This article focuses on progress in the SAA field since our 2020 review (Chem. Rev.2020, 120, 12044-12088.), while incorporating earlier foundational studies where relevant. We first examine the fundamental principles governing SAA formation, stability, electronic structure, reactivity, and selectivity, drawing on insights from experimental single-crystal model systems and theoretical studies. We then review the application of SAAs in a wide range of industrially important reactions, including hydrogenation, dehydrogenation, selective oxidation, water-gas shift, Fischer-Tropsch synthesis, and dry reforming, among others. Beyond thermal catalysis, SAAs demonstrate great promise in electrocatalysis and plasmon-driven chemistry. Their structurally simple active sites have also enabled the rational design of novel catalysts and promoters that challenge conventional catalytic intuition. Looking ahead, recent advances in computing, including machine-learning potentials, offer the opportunity to explore vast compositional spaces and discover new alloy chemistries for challenging reactions using the SAA concept.