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.