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 (WO2[OH]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. The tungsten oxides were first reduced by hydrogen to WO2 and finally to tungsten powder. This process also produces hydrone and WO2(OH)2, which is an auto‐catalyst. The reduction time for tungsten oxides mostly depends on the crystal structure of the raw material, the temperature and flow rate of hydrogen. The microstructure for product of different tungsten oxides also varies very different.