Hot carrier photochemistry on metal nanoparticles

The last decade has seen a growing number of reports utilizing illuminated metal nanoparticles to drive chemical reactions of industrial and societal importance. Putting light to use in chemical reactions is an important alternative to petroleum, given its ubiquity as a sustainable energetic medium. Light also unlocks electronic contributions to chemical reactions through the generation and action of hot carriers on molecular adsorbates that are unavailable in traditional thermochemical transformations. In this Perspective, we will provide a pedagogical overview of important techniques and results from decades of surface science research that have built the foundation of modern studies on hot carrier photochemistry. Advances in nanoscience and heterogeneous catalysis have since introduced new materials, particularly metal nanoparticles that sustain collective electronic oscillations under illumination (plasmon resonances), to be exploited as potent photocatalysts. Plasmonic photocatalysts have strong optical absorption and, through Landau damping, can be engineered to maximize hot carrier generation within a given volume and applied to reactions of interest. Plasmonic hot carriers can induce excited electronic, vibrational, and rotational states in adsorbates that promote unexpected surface reactivities in the presence of light. We will address open questions regarding energy transfer, catalyst design, and possible implementation beyond laboratory scales. Throughout this Perspective, reactions critical to sustainability will be addressed given the urgent need to decarbonize the energy and chemical industries.