Alumina-Supported Single-Atom Catalysts: Rational Design, Synthesis Strategies, and Functional Applications

Support materials determine the stability and electronic characteristics of active metal sites, offering a foundation for customizing heterogeneous catalysts for specific functional applications. Alumina (Al₂O₃) is an irreducible oxide and an excellent support material in industrial catalysts because of its exceptional thermal stability, structural versatility, and affinity for metal anchoring and molecule adsorption. Isolated metal atoms having unique electronic structure enable 100% atom utilization efficiency and represent the cornerstone of single atom catalysts (SACs). Although the concept of SACs has advanced drastically, SACs on Al₂O₃ supports remain a relatively nascent area of research. This review systematically examines the landscape of SACs supported on Al₂O₃, assessing the synthetic strategies employed, expounding their structural characteristics, metal-support interactions, and applications. Commencing with an overview of the various transitional phases of Al₂O₃, we explore the critical role of surface defects and penta-coordinated Al³⁺ sites in coordinating and stabilizing metal atoms. Furthermore, we correlate these structural features to their catalytic performance, elucidated through advanced characterization techniques such as X-ray absorption spectroscopy and atomic-resolution electron microscopy. Through a comprehensive discussion, the review attempts to provide a clear and systematic explanation of the current accomplishments, obstacles, and future prospects in the emerging research field of single-atom catalysis.