Solar-vapor generation with 69% energy conversion efficiency in hollow-mesoporous plasmonic nanoshells

Harnessing solar energy at a high efficiency and a low cost remains challenging. The advent of nanotechnology enabled new solar-thermal techniques where plasmonic nanoparticles (NPs) in a volumetric dispersion are used to generate steam locally without a significant heat loss into the entire bulk, thereby alleviating the need for an extensive thermal insulation. Nanoparticle-assisted solar-vapor generation was recently demonstrated using SiO
2
/Au core/shell NPs at 1000× solar irradiance at air mass (AM) 1.5, showing an energy conversion efficiency of 24% [1]. Here, we achieve solar-vapor generation at 69% efficiency at 10× AM 1.5 by combining plasmonics with mesoporous thermal cavities, exploiting the extended active surface and nearly neutral buoyancy [Fig. 1(a)].