Novel strategy of highly efficient solar-driven water evaporation using MWCNTs-ZrO2-Ni@CQDs composites as photothermal materials

Abstract

Solar-driven water evaporation is a promising technology for high efficiency water purification by absorbing solar energy and converted into localized heat. Herein, we report a low-cost approach for developing a novel photothermal materials based on combination of ZrO2 nanoparticles (NPs) with Ni doped carbon quantum dots (Ni@CQDs) and multi-walled carbon nanotube (MWCNT) coated on melamine foam (MF) surface. The formation of Ni@CQDs was confirmed by red-shift absorbance and fluorescence. Moreover, the shift in XRD diffraction angle indicated the Ni@CQDs incorporated into the ZrO2 and carbon framework of MWCNT. The composite absorber demonstrates excellent solar-water evaporation rate of 1.95 kg m−2 h−1 and high evaporation efficiency of 89.5%, which is ten-fold improvement as compared to pure water (0.19 kg m−2 h−1) under 1-Sun irradiation. The enhancement in evaporation rate is mainly attributed to the strong light absorption of 94% and extremely low thermal conductivity of MWCNT/ZrO2/Ni@CQDs (0.038 W m−1 K−1). The composite absorber capable of continuous operation of 6 cycles under 1-Sun irradiation, indicates high durability and completely reduced organic dyes (99.8%). Accordingly, the novel design of MWCNT/ZrO2/Ni@CQDs as composite absorber as high performance solar-driven water evaporation and wastewater purification.