High H2 sensing performance in hydrogen trititanate-derived TiO2

Two types of H2Ti3O7 powders were prepared by ion exchange and hydrothermal methods, and the H2 sensing properties of the H2Ti3O7-derived TiO2 sensors were examined. In the ion exchange method, Na2Ti3O7 was first synthesized via a solid-state reaction, and H2Ti3O7 was obtained from Na+/H+ exchange on Na2Ti3O7. H2Ti3O7 was also prepared via a hydrothermal reaction of TiO2 powder in a NaOH solution. The morphology, size, and phase evolution of H2Ti3O7 were found to be strongly dependent on the preparation methods. The TiO2 sensors fabricated by the H2Ti3O7 powders calcined at 700 °C (ion exchanged) exhibited an excellent gas response (S = 30,000) to 1.0% H2/N2 at 500 °C, which was three orders of magnitude higher than that of the hydrothermally synthesized powder and commercial anatase powder even though its specific surface area was smaller. The higher H2 gas response in the TiO2 sensor derived from the ion exchanged H2Ti3O7 is discussed in terms of the metastable β-TiO2 and anatase phases.