Exploiting the Synergy between Thermal and Nonthermal Effects
Quantifying thermal and non-thermal effects in plasmonic catalysis provides a better understanding of the reaction mechanism.(Fig 1A, B) The complex nature of thermal effects under reaction conditions makes it challenging. Being able to separate the thermal and non-thermal effects in plasmonic catalysis is a major step in understanding the reaction mechanism. However, the overall reaction enhancement from light is a combination of all factors. In addition, the non-thermal effect is supposed to be restricted to the surface of the catalysts where the catalysts are directly illuminated by light while the thermal effect can penetrate deeper into the catalyst layer due to thermal transport. In order to achieve the maximum light enhancement in plasmonic catalysis, we studied the contributions from both thermal and nonthermal effects to achieve the largest light enhancement for methane production.
In this work, we found that the complex thermal effects are influenced by the external heating input, light intensity, and the number of catalysts inside the reactor. By looking at the total light efficiency, we combined both the thermal and nonthermal effects to achieve the maximum enhancement at 325℃, 0.76W·cm-2 UV light with 20 mg catalyst in our current reactor system (Fig 1C).
Figure 1: The schematic diagram of (A) the reactor setup, and (B) thermal and nonthermal effects from plasmonic excitation. (C) The calculated efficiency production rate of CH4 using different amounts of catalyst.
Understanding and Controlling Light Distribution in Plasmonic Catalysis
The use of waveguide structures to enhance photocatalysis has recently been garnering significant attention. The manipulation of light by support structures is applicable beyond photochemical catalysis and should be harnessed for plasmonic and photothermal catalysis as well. This project is mainly focused on the synthesis, evaluation, and optimization of novel microstructured catalyst supports the whose ability to manipulate light will be applicable to a wide variety of light-catalyzed reactions including plasmonic CO2 hydrogenation and photothermal ammonia synthesis. First, diffuse scattering supports will increase light penetration depth and by extension maximum beneficial source intensity. To achieve this, a recently developed boron nitride “Artificial fog” microtube structure with incredibly low loss scattering capability and thermal and chemical stability is in the process of being replicated and adapted to the catalytic application by the integration of rhodium plasmonic nanoparticle catalysts.
