Controlling the Composition of Nanosize Hexagonal WO₃ for Gas Sensing

Hexagonal (h-) WO3 was prepared through heating hexagonal ammonium tungsten bronze (HATB), (NH4)(0.07)(NH3)(0.04)(H2O)(0.09)WO2.95. By adjusting the heating temperature and atmosphere of HATB, we could control the oxidation state of tungsten atoms and the residual NH3/NH4+ content in h-WO3. The as-produced h-WO3 nanoparticles with different composition were tested as gas sensors and the effect of composition on gas sensing properties was studied. Our results showed that oxidized h-WO3 had the best sensitivity to H2S.