Janus Emulsion Solar Concentrators as Photocatalytic Droplet Microreactors

Abstract Efficiently harvesting and conveying photons to photocatalytic reaction centers is one of the great obstacles in photocatalysis. To address this challenge, a new approach is reported that is based on employing biphasic complex emulsions as droplet‐based solar concentrators. Specifically, substrates and photocatalysts are compartmentalized into the confined space of Janus emulsion droplets comprised of a hydrocarbon partially encapsulated inside fluorocarbon oil with a large refractive index contrast. Optical confinement of the incident light due to total internal reflection at the concave internal interface of the biphasic emulsion droplets leads to a strong increase of the light intensity inside the reaction medium. In addition, the high gas solubility within the outer fluorocarbon phase promotes oxygen delivery in photocatalytic oxidation reactions. Both effects mutually contribute to a strong performance increase of a series of homogeneous and heterogeneous photocatalytic reactions even under diffuse sunlight conditions.