Identifying signatures of thermal and non-thermal reaction pathways in plasmon induced H2 + D2 exchange reaction

In this work we demonstrate a strategy for identifying experimental signatures of thermal and non-thermal effects in plasmon mediated heterogeneous catalytic chemistry, a topic widely debated and discussed in the literature. Our method is based on monitoring the progress of plasmon induced (or thermally driven) reaction, carried out in a closed system, all the way to equilibrium. Initial part of evolution of the reaction provides information about kinetics, where as at later times the equilibrium concentrations provide information about effective temperature at the reaction sites. Combining these two pieces of information we estimate the activation energies. Using this strategy on H2 (g) + D2 (g) <--> 2 HD(g) isotope exchange reaction, catalyzed by Au nanoparticles under thermally driven and light induced conditions, we estimate the activation energies to be 0.75 ± 0.02 and 0.21 ± 0.02, respectively. These vastly different activation energies observed are interpreted as signatures of different reaction pathways followed by the system under thermally driven and light induced conditions.