Single-step room temperature synthesis of vanadium oxide nanosheets for seawater/wastewater purification by photothermal evaporation under one sun illumination

Abstract

Vanadium dioxide has excellent absorbance in near-infrared (NIR) wavelengths making it a perfect candidate for photothermal applications based on solar energy. However, up to date, it was mainly applied in a lithium-ion battery. This study is for the second time, to utilize VO₂-based nanomaterials as a photothermal material for solar steam generation to purify seawater and wastewater. The study has proposed a straightforward and promising room temperature approach to synthesize a mixture of two vanadium oxide nanosheets with a major fraction of VO₂ (B) nanosheets with the major part for VO₂.nH₂O and a minor fraction of V₂O₅.nH₂O which have demonstrated excellent photothermal capability for water purification. The highest steady state temperature of ∼ 87 °C was reported by the synthesized nanosheets that were spray coated on cellulose fabric for the solar absorption purpose under one sun illumination for water purification. The as-prepared photo absorber was capable of reaching the highest steady temperature at high speed (within 10 minutes). The synthesized 2D VO₂/V₂O₅.nH₂O nanosheets and cellulose fabric combination of solar steam generator gained a competitive evaporation rate of 1.31 kgm^-2h⁻¹ and a percentage efficiency of 89.7% under one sun illumination. The current approach was successfully applied to three real-world samples to obtain clean or drinking water. All three samples showed excellent improvements in their water quality compared with their initial states in a single distillation. Two samples can even reach the quality of World Health Organization (WHO)-recommended standards for drinking water. The current approach has opened a new platform for the utilization of VO₂-based nanosheets for obtaining clean water from seawater and wastewater by solar energy utilization.