This review introduces the concept of single-atom-layer (SAL) metallization in plasmonic semiconductor systems. It discusses how this concept addresses the kinetic challenges of hot electrons in photocatalytic reactions from the aspects of generation, separation, and transfer, and proposes design strategies for novel plasmonic semiconductor photocatalysts with distinct SAL structures, aiming to advance photocatalytic processes through atomic-level engineering.

Over the past decade, plasmonic semiconductors have emerged as a promising material family for diverse photocatalytic applications, spanning solar energy conversion to environmental remediation. The unique localized surface plasmon resonance (LSPR) enables these materials to harvest abundant low-energy photons and generate high-energy hot-carriers (electrons or holes). However, these hot carriers face critical challenges in photocatalytic applications, including inefficient excitation processes, ultrashort carrier lifetimes, and sluggish carrier transfer to reactants. This review introduces the concept of single-atom-layer (SAL) metallization on plasmonic semiconductors as a strategy to simultaneously address the aforementioned challenges. How SAL metallization influences light harvesting processes and hot-electron kinetics in plasmonic semiconductors is systematically discussed, and the synergistic effects of heterometallic atoms within SAL on photoreduction reactions are analyzed. Building upon these insights, future research directions are proposed that explore SAL integrated with frustrated Lewis pairs, high-entropy configurations, and nonmetallic surface modifications on plasmonic semiconductors. Additionally, this review envisions the development of heterojunction systems composed of metallic and nonmetallic SAL-coated plasmonic semiconductors, highlighting their potential for advanced photocatalytic applications.