Disentangling Plasmonic Enhancement of Electronic and Thermal Effects in Catalysis Using In Operando X-ray Diffraction

Photocatalysis by illumination of plasmonic catalytic nanostructures may offer energetically efficient and highly selective alternatives to state-of-the-art thermocatalysis, which typically requires significant energy input for a high temperature operation. While many demonstrations of plasmonic photocatalysis exist, disagreement remains regarding the mechanism(s). Originally, nonthermal (so-called “hot”) carriers appeared responsible for the catalysis, but recently heating emerged as a likely primary mechanism. Distinguishing between these two mechanisms is difficult since it requires accurate knowledge of the catalyst temperature. Here, we report in operando X-ray diffraction under illumination to unambiguously determine the average temperature of the catalyst during CO oxidation by measuring lattice parameters of both the catalytic nanoparticles and their oxide support. By simultaneously measuring the reaction rate, we find that “hot” carriers play no role in this reaction with this catalyst. Our experimental design provides a generally applicable method for the determination of the catalytic mechanism and paves the way for future chemical studies of catalytic plasmonic nanostructures.