efficiency in solar steam generation by 2D photothermal materials has
approached its limit. In this work, we fabricated 3D cylindrical
cup-shaped structures of mixed metal oxide as solar evaporator, and the
3D structure led to a high energy efficiency close to 100% under one-sun
illumination due to the capability of the cup wall to recover the
diffuse reflectance and thermal radiation heat loss from the 2D cup
bottom. Additional heat was gained from the ambient air when the 3D
structure was exposed under one-sun illumination, leading to an
extremely high steam generation rate of 2.04 kg m−2h−1.
The 3D structure has a high thermal stability and shows great promise
in practical applications including domestic wastewater volume reduction
and seawater desalination. The results of this work inspire further
research efforts to use 3D photothermal structures to break through the
energy efficiency limit of 2D photothermal materials.