Untangling Thermal and Nonthermal Effects in Plasmonic Photocatalysis

This chapter introduces a methodology to distinguish the thermal and nonthermal contributions in an illuminated, plasmon-enhanced catalyst. Although nonthermal effects in light-driven reactions are deservedly drawing much attention, photothermal effects may prove to be even more beneficial because of the way illumination can tailor thermal profiles within a catalyst. The technique presented here extracts the effective thermal and nonthermal reaction rates under illumination by simultaneously measuring the total reaction rate and the top- and bottom-surface temperatures of the catalyst bed. Using these measured temperatures, a simplified model of the catalyst thermal profile and effective thermal reaction rates may be deduced for the illuminated catalysts. Ruthenium and rhodium photocatalysts with intrinsic plasmonic and catalytic properties for NH₃ synthesis and CO₂ hydrogenation were respectively used to illustrate this technique and examine thermal, photothermal, and nonthermal reaction rates. Through innovative experimental techniques, the thermal and nonthermal contributions may be systematically evaluated to understand underlying synergistic mechanisms in plasmonic photocatalysis and extract the nonthermal contribution from the total measured reaction rate.