Soft chemical synthesis and crystal structure of novel hydrogen titanium oxide H₂Ti₁₂O₂₅

抄録

We have successfully prepared H₂Ti₁₂O₂₅ by soft chemical synthetic technique using Na₂Ti₃O₇ as a precursor material. The crystal system is the monoclinic system, space group C2/m, and its lattice parameters were refined to be a = 12.4485(2) Å, b = 3.74414(3) Å, c = 19.9523(5) Å and β = 95.244(2)° by electron diffraction pattern and powder X-ray diffraction pattern. The crystal structure of H₂Ti₁₂O₂₅ and lithium-ion inserted H₂Ti₁₂O₂₅ were estimated by Monte Carlo method for the first time. As a result, the formula of the lithium-ion inserted state was Li₁₀H₂Ti₁₂O₂₅. From these results, theoretical capacity was estimated to be 274.6 mAh/g. The total protonic conductivities in H₂Ti₁₂O₂₅ was estimated to be σ_total = 8.71 × 10⁻⁹ S cm⁻¹ at room temperature from the results of AC-impedance. The estimated band gap for H₂Ti₁₂O₂₅ is about 3.34 eV, the value of which is very similar to those for Na₂Ti₆O₁₃ and Li₂Ti₆O₁₃.