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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.