Laser-Synthesized Rutile TiO₂ with Abundant Oxygen Vacancies for Enhanced Solar Water Evaporation

Abstract

Titanium dioxide (TiO2) as a common photothermal material usually faces with low photothermal conversion efficiency, mainly owing to the little utilization of visible (Vis) and near-infrared (NIR) light in the solar spectrum. Introducing oxygen vacancies is an effective strategy for narrowing its bandgap and thus enhancing the light absorption capacity. However, traditional approaches are always not energy-efficient or unable to create enough oxygen vacancies. Herein, laser ablation in liquid (LAL) was successfully employed to prepare rutile TiO2 nanoparticles (NPs) with abundant oxygen vacancies in one step, which were then assembled into the self-floating evaporator. Our experimental results demonstrate that the existence of oxygen vacancies narrows the bandgap and forms conduction band tail states, leading to significant improvements of light absorbance and photothermal conversion efficiency. Moreover, the light trapping structure of nickel foam (NF) support also contributes to the high solar absorption of laser TiO2 (L-TiO2)/NF. Eventually, the L-TiO2/NF evaporator realizes an excellent water evaporation rate of 1.25 kg m–2 h–1 and light-to-water evaporation efficiency of 78.5% under one-sun irradiation, which are both 1.81 times than those of commercial TiO2 (C-TiO2)/NF and even surpass those of most recently reported titanium oxide-based evaporators.