Study on mechanism of hydrogen adsorption on WO3, W20O58, and W18O49

The density functional theory (DFT) calculation of hydrogen adsorption on tungsten oxides and calculation of the crystal structure of WO₃, W₂₀O₅₈, and W₁₈O₄₉ were performed_. These calculations suggest that the length of W-O bonds in WO₃ are 1.913 Å, the length of 66% W-O bonds in W₂₀O₅₈ is 1.8 to 1.9 Å, and the length of 43.48% W-O bonds in W₁₈O₄₉ is longer than 2.0 Å. The hydrate (WO₂OH]₂), as an autocatalyst in the hydrogen reduction process, was found in the particular adsorption configuration of W₁₈O₄₉. The WO₃ and W₂₀O₅₈ were completely reduced within 40 to 60 minutes at a temperature of 1000°C and at a hydrogen flow rate of 200 mL/min, while W₁₈O₄₉ was completely reduced within 20 to 40 minutes. The phase composition and micromorphology of raw material and production were studied by both X-ray diffraction analysis (XRD) and FE-SEM technology. The differences of the mechanism of hydrogen adsorption on WO₃, W₂₀O₅₈, and W₁₈O₄₉ were explored based on the density functional theory calculation and the hydrogen reduction experiments.