Highly Efficient Solar Steam Generation by W18O49@PVA Gels.

Oxygen-deficient tungsten oxide W18O49 was synthesized through lattice oxygen escaping at high temperature in N2 atmosphere. The temperature and inert atmosphere were critical conditions to initiate the lattice oxygen escaping to obtain W18O49. The large amount of oxygen vacancies supports its performance in photothermal conversion. The synthesized tungsten oxides were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible absorption spectroscopy (UV-Vis). The composite gel was fabricated by the insertion of oxygen-deficient tungsten oxide into PVA-based gel, which was cross-linked by glutaraldehyde. The PVA-based gel ensures a matched water supply speed with that of the evaporation rate due to its hydrophilic nature. The result of the solar steam generation shows that the W18O49-PVA gel (steam generation rate 2.65 kg m-2 h-1) was faster than that of the pure PVA gel.