Metal single-atom catalysts (SACs) have emerged as a focal point of research, captivating the scientific community due to their distinctive electronic properties and unparalleled catalytic prowess in the realm of heterogeneous catalysis. However, their significance transcends their role as mere active sites. Recent investigations have illuminated the multifaceted capabilities of metal single atoms as catalyst promoters and precursors, paving the way for the engineering of highly efficient heterogeneous catalysts. Single-atom promoters not only enhance the stabilization of active metals and tailor the support material, but regulate the reactive interfacial structure, eventually tuning the catalytic performance. Furthermore, SACs were also used as catalyst precursors to design new catalyst active sites. During the pretreatment or catalytic reaction, the structure of the metal single sites is changed significantly and transformed into the new and more active state, which improve the adsorption and reactive ability of reactants or intermediates. In this critical review, we comment the recent development of metal SACs used as catalyst promoters/precursors in engineering heterogeneous catalysts, including thermal catalysis and electrocatalysis. Furthermore, the dynamic evolution of the SACs during the pretreatment or catalytic reaction is also discussed. Finally, we provide our insight to potentially guide the future development on this emerging field.

金属单原子催化剂（SAC）已成为研究的焦点，因其独特的电子特性和在多相催化领域无与伦比的催化能力而吸引了科学界的关注。然而，它们的重要性超出了它们作为单纯活性位点的作用。最近的研究阐明了金属单原子作为催化剂促进剂和前体的多方面能力，为高效多相催化剂的工程化铺平了道路。单原子促进剂不仅可以增强活性金属的稳定性并定制载体材料，还可以调节反应性界面结构，最终调整催化性能。此外，SAC还被用作催化剂前体来设计新的催化剂活性位点。在预处理或催化反应过程中，金属单中心的结构发生显着变化，转变为新的、更活泼的状态，从而提高了反应物或中间体的吸附和反应能力。在这篇批判性评论中，我们评论了金属 SAC 在工程多相催化剂（包括热催化和电催化）中用作催化剂促进剂/前体的最新发展。此外，还讨论了预处理或催化反应期间 SAC 的动态演化。最后，我们提供了我们的见解，以指导这一新兴领域的未来发展。