Production of clean water from seawater
and wastewater
is significant through photothermal evaporation using unlimited solar
energy. Here, we constructed a double-layer-structure evaporator (DLSE)
consisting of nickel foam@reduced graphene oxide–carbon nanotube
(NF@RGO–CNT) as a solar absorber and an expanded polyethylene
foam (EPE)/thermoelectric (TE) module as a heat insulator, which was
used in various water purification processes and simultaneous electricity
generation. The reduced graphene oxide covered on the surface of nickel
foam increases broad-band absorption of sunlight and weakens the thermal
emittance, and its coarse surface decreases the reflectance of light,
which ensures the largest photo-to-heat conversion efficiency. Compared
with the pristine nickel foam, NF@RGO–CNT has a low thermal
conductivity to achieve localized high temperatures, which favors
the evaporation of water on the interfacial surface. As such, a high
water evaporation rate of 1.37 kg m–2 h–1 together with a photothermal conversion efficiency of 96.4% was
achieved over the NF@RGO–CNT under 1 kW/m2. Meanwhile,
the thermoelectricity during solar evaporation is generated by utilizing
the TE module instead of EPE, in which a maximum output power of 0.251
W m–2 was achieved under 1 kW/m2. In
addition, clean water can be produced using DLSE equipment from various
water sources such as brine water, organic wastewater, seawater, and
lake water, in which the quality of the evaporated water is better
than drinkable water standard, and the evaporation performance is
comparable to that of pure water.