Single-Atom Catalysis

Catalysis lies at the core of chemical science and technology and underpins most industrial chemical transformations. It is estimated that well over 80–90% of all chemical products are manufactured using at least one catalytic step. Beyond its established industrial role, catalysis has become a central pillar of sustainable chemistry, enabling reductions in energy consumption, improved atom efficiency, lower greenhouse-gas emissions, and the development of alternative energy technologies.

In recent years, the demand for atom-efficient, selective, and environmentally benign catalytic systems has intensified. This demand has driven the emergence of single-atom catalysts (SACs) as a distinct and rapidly expanding class of materials. By isolating catalytically active metal centers at the atomic scale, SACs challenge traditional distinctions between homogeneous and heterogeneous catalysis and offer unprecedented opportunities to maximize metal utilization, tune electronic structure, and control reaction pathways. Despite their growing importance, the conceptual foundations of SACs remain scattered across specialized literature, often presented with a strong emphasis on either synthetic details or advanced theoretical formalisms. This fragmentation creates a clear need for a concise, concept-driven introduction that integrates fundamental catalysis principles with the specific challenges and opportunities of atomically dispersed active sites.

This primer was written for readers who are curious about how catalysis operates at its most fundamental level, and why controlling matter down to a single atom has become such a powerful idea. Whether you are a student entering the field, a researcher from a neighboring discipline, a practitioner seeking a deeper conceptual framework, or simply a curious reader with a passion for chemical science, this primer aims to bridge well-established catalytic principles with the emerging world of atomically precise catalysts. This primer was planned to provide a conceptual and mechanistic introduction to SACs, starting from the foundations of catalysis and gradually progressing toward modern SAC concepts (CHAPTER 1), the experimental techniques used to validate them (CHAPTER 2), design strategies (CHAPTER 3), and inherent limitations and future perspectives (CHAPTER 4). The authors have deliberately adopted the clearest, most accessible, and most didactic language possible throughout. Rather than serving as an exhaustive reference or a mathematically formal treatise, this work is intentionally structured as a didactic puzzle, in which each piece builds upon the previous one. The narrative emphasizes physical intuition and well-defined concepts, translating the field's complexity into a concise, accessible, and continuous reading experience while deliberately avoiding heavy theoretical formalism.

In practice, this primer can be used in different ways. It may be read sequentially, as a guided introduction that builds fundamental concepts step by step, or consulted selectively, with individual chapters serving as entry points to specific aspects of catalysis and SACs. For students, it can function as a companion text to courses in catalysis and, to some extent, materials chemistry. For researchers, on the other hand, it provides a structured framework for the scientific planning of SAC-based systems, encompassing catalyst design, characterization strategies, and potential applications. In addition, the primer incorporates the most up-to-date literature available at the time of publication, offering a starting point for deeper exploration. More broadly, it is intended as a reference for developing intuition, something to return to when designing experiments, interpreting data, or questioning assumptions, rather than as a manual to be memorized.