Recent advances in “top-down” synthesis strategies for single-atom catalysts

Single-atom catalysts (SACs) have emerged as the forefront of catalysis research due to their maximum atomic utilization efficiency, unique electronic structures, and exceptional performance in diverse reactions. By anchoring isolated metal atoms on supports like carbon-nitrogen matrices or metal oxides, SACs bridge the gap between heterogeneous and homogeneous catalysts, combining easy recyclability with highly uniform active sites. However, their large-scale deployment has long been hindered by synthesis challenges such as low metal loading, poor stability, and high costs. SAC synthesis is typically divided into "bottom-up" and "top-down" approaches. The USTC team’s review emphasizes the transformative advantages of the top-down strategy (higher metal loading, cost-effectiveness, scalability, and superior atomic utilization).

This review outlines the general top-down strategy for manufacturing SACs from different precursors. Metal nanoparticles are broken down into single atoms through thermal atomization, gas-phase assistance (e.g., CH₄, PH₃), or laser ablation, and anchored by supporting defects (e.g., N-doped carbon, metal oxides). Large pieces of metal (e.g., Ni foil, Cu foam) generate individual atoms through solid-state thermal diffusion, high-temperature shock or gas-assisted atomic emission (e.g., NH₃), and then these atoms are captured on the support. Commercial metal oxides (such as Cu₂O, RuO₂) or sulfides (such as CdS) are converted into single metal atoms through thermal radiation or cation exchange reactions. Metal-organic frameworks have the advantages of adjustable structure and large specific surface area, and can be directly converted into SACS through calcination.

This review also points out some key challenges faced by top-down single-atom catalysts and outlines the future development directions. It provides a crucial roadmap for researchers in catalysis, materials science, and energy, making the next generation of high-performance and practical catalysts possible.