Probing Spatial Energy\nFlow in Plasmonic Catalysts\nfrom Charge Excitation to Heating: Nonhomogeneous Energy Distribution\nas a Fundamental Feature of Plasmonic Chemistry

Plasmonic catalysts use light to drive chemical reactions.\nOne\ncritical question is how light energy moves at nanoscales in these\ncomplex systems, leading to chemical transformations. In this contribution,\nwe map out this energy flow by developing approaches to measure spatial\ntemperature distributions in heterogeneous plasmonic catalysts, consisting\nof three-dimensional networks of plasmonic nanoparticles anchored\non an oxide support. We survey the local temperatures of molecules\nadsorbed on catalytically active plasmonic nanoparticles, the nanoparticles\nthemselves, and the catalyst support, under steady-state continuous-wave\nillumination. We reveal the existence of large temperature gradients,\nin which the local temperatures of the molecules, nanoparticles, and\nthe surrounding environment can vary greatly. We show that these temperature\ngradients are a natural consequence of plasmon relaxation, involving\nthe interconversion between electromagnetic light energy, electronic\nexcitations, and heating of various entities as these electronic excitations\nrelax. The presence of these gradients is a fundamental and unique\nfeature of gas-phase plasmonic catalysis.