Plasmonic photocatalysis: mechanistic principles, spectroscopic characterization, and applications for solar-to-chemical conversion

Plasmonic photocatalysis has attracted considerable interest because localized surface plasmon resonances (LSPRs) enable efficient harvesting of visible-to-near-infrared light and enhance photocatalytic activity. Various mechanisms have been proposed to clarify the enhanced effect of plasmonic photocatalysis, such as near-field enhancement, hot-carrier generation and injection, plasmon-induced resonance energy transfer, and photothermal heating, leading to persistent thermal versus non-thermal debate, which greatly hinders the rational design of plasmonic photocatalysts. In this Review, we try to address these issues by presenting a more connected framework of plasmonic photocatalysis. We start from the fundamental principles of localized surface plasmon resonance decay and relate it to the four main enhancement mechanisms. Then, we connect these mechanisms with advanced characterization techniques and catalytic performance. We present an integrated spectroscopic framework employing transient absorption spectroscopy, surface-enhanced Raman spectroscopy, tip-enhanced Raman spectroscopy, and time-resolved X-ray methods to separate, identify and validate overlapping plasmonic energy-transfer pathways. By comparing model reactions with practical systems like water splitting, CO 2 reduction, and ammonia synthesis, we show that the dominant mechanism is not an inherent property of the material; instead, it depends on reaction conditions, excitation wavelength, and the local environment. This challenges the usual classification of plasmonic catalysts as either thermal or non-thermal, which may be too simplified. It also suggests the possibility of systems that can be tuned depending on conditions. Finally, we point out key challenges, including scalable fabrication, long-term stability, and the need for artificial intelligence-driven approaches.