Nanoscale Energy Balance of Plasmonic Antenna-Reactor Catalyst for Light Driven Reactions: Role of Hot carriers vs. Photo-thermal Effect

The antenna-reactor configuration is an ideal plasmonic catalytic system in which a light harvesting nano-antenna captures and concentrates photonic energy, and provides it to the catalyst for plasmon mediated catalysis. In fact, all plasmonic catalytic system has this synergy between the plasmonic and the catalytic component. In plasmonic catalysis, the relative contribution of hot carriers and the mere photothermal effect is a matter of much debate. In this analysis, the energy balance of the antenna-reactor system is dissected to unravel mechanistic insights, as well as to reveal the key factors affecting the catalytic process. Based on existing benchmark experimental data, the analysis shows that utilization of <1% of absorbed energy for hot carrier driven activity, resulting in a 4-fold enhancement in the rate constant of plasmon-enhanced dehydrogenation. For the disentanglement of thermal effects, a very high light intensity (>10 sun intensity for 4 cm2 films) or system size (>144 cm2 film for 1 sun intensity) is required to attain accurately measurable temperatures. Analysis of different nano-configurations demonstrates the clear merit of the antenna-reactor photocatalyst design. Generally, it is shown that similar to energy balance of large scale chemical processes, the energy balance of optical nanoscale systems can uncover the energetics of the micro-processes at nanoscale, irrespective of the details of the underlying temporal quantum processes. The combination of classical electromagnetic analysis and experimental data can thus uncover useful quantitative insights into such systems.