High efficiency solar desalination and dye retention of plasmonic/reduced graphene oxide based copper oxide nanocomposites

Abstract

Water desalination via solar-driven interfacial evaporation is one of the most essential technologies to limit the problem of global freshwater scarcity. Searching for a highly efficient, stable, eco-friendly, and cost-effective solar-absorber material that can collect the full solar spectrum is critically important for solar steam generation. This study reports the development of a new solar thermal evaporation system based on plasmonic copper oxide/reduced graphene oxide (rGO). The silver nanoparticles in the composite exhibit a very strong solar absorption. Also, rGO and CuO nanoparticles offer excellent thermal absorptivity. Polyurethane was used as the support and as a thermal insulator. Moreover, filter paper was used for fast water delivery to the surface of the solar absorber. Ag/CuO-rGO nanocomposite is manifested to be one of the most efficient solar-absorbers reported to date for solar desalination which exhibits an average 2.6 kg m^-2 h^-1 evaporation rate with solar thermal efficiency up to 92.5% under 1 sun irradiation. Furthermore, the composite has excellent stability and durability as it displays stable evaporation rates for more than 10 repeated cycles in use, with no significant decrease in the activity. Besides, the successful removal of various organic dyes from contaminated water is also revealed, resulting in the production of clean condensed freshwater. Finally, this work commences a new avenue of synthesizing cost-effective thermal absorbers based on metal oxides.

Scheme 1. Schematic of solar steam generation device based on the prepared photothermal membranes.

Fig. 1. (a) FT-IR spectra and (b) UV-vis spectra of GO, CuO-rGO, Ag-rGO and Ag/CuO-rGO.

Fig. 2. XRD pattern of GO, CuO-rGO, Ag-rGO and Ag/CuO-rGO.

Fig. 3. TEM images of (a) GO, (b) CuO-rGO, and (c) Ag/CuO-rGO.

Fig. 4. (a) Optical image of the solar evaporator device, (b) mass changes for the different solar absorbers, and (c) mass change of pure and saline water for Ag/CuO-rGO membrane under 1 sun illumination.

Fig. 5. IR thermal images of (a) Ag/CuO-rGO, (b) Ag/rGO, (c) CuO-rGO, (d) GO, (e) CuO, and (f) filter paper after 60 min under 1 sun illumination.

Fig. 6. Temperature change at the surface of the absorber for different samples (a) 60 min with the lamp on, and (b) 10 min the lamp turned on and then turned off till reaching room temperature. (c) and (d) IR thermal images under 1 sun illumination of Ag/CuO-rGO at zero minutes and after 60 minutes, respectively.

Fig. 7. (a) The evaporation efficiency of different absorbers (b) evaporation rate of Ag/CuO-rGO for different water salinity under 1 sun illumination for 60 min.

Fig. 8. (a) Concentration metal ions, (b) UV-vis spectra of dyes, before and after the steam generation experiment, (c) recyclability test of the Ag/CuO-rGO sample during 10 cycles under constant illumination of 1 sun for 60 min, and (d) image of amount of precipitated salts emerged on the surface of evaporator after 1 h under 1 sun illumination in 20 wt% saline.