Revisiting thermal and non-thermal effects in hybrid plasmonic antenna reactor photocatalysts

Photon-driven catalytic reactions have long been explored as a way to reduce emissions by replacing fossil-fuel-derived process heat with solar energy. Light-harvesting plasmonic metal nanoparticles are promising photocatalysts because they can drive kinetically unfavorable reactions through combined non-thermal (hot charge carrier) and photothermal effects under illumination. Understanding the interplay between these effects is critical for optimizing these materials for sustainable photochemical production processes. Unfortunately, the simultaneous presence of these two mechanisms under relevant photocatalytic operating conditions has led to fierce debate in the plasmonic catalysis community about the relative contributions of each. This perspective examines frequently overlooked concepts when attempting to disentangle thermal and non-thermal effects in plasmon-driven, gas-phase heterogeneous photocatalysis. We focus on the rising use of hybrid plasmonic (antenna-reactor) materials, which combine light harvesting and catalytically active metal components. We postulate that the addition of second metal sites further complicates the distinction between thermal vs. non-thermal effects. Specifically, changes in light absorption, the energy and lifetime of charge carriers, nanoscale heating, and dynamic catalyst restructuring upon the creation of multicomponent systems need to be considered. Throughout this perspective, we highlight key questions that must be resolved to address these issues. We conclude by proposing pathways to bridge the fundamental and applied research gap to accelerate the potential integration of plasmonic catalysis into large-scale chemical processes.