Structural and electrochemical properties of hydrogen titanium oxides

Abstract

Abstract Hydrogen titanium oxide H 2 Ti 6 O 13 was prepared from Li 2 Ti 6 O 13 as a parent compound via Li + /H + ion exchange in acidic solution at 60 °C. It crystallizes in the monoclinic system, space group C 2/ m , and the lattice parameters of a = 14.6604(3) A, b = 3.74109(8) A, c = 9.2487(2) A, and β = 96.956(2)°. The crystal structure of H 2 Ti 6 O 13 was refined to the conventional values of R wp = 3.12% and R p = 2.45% with a fit indicator of GOF = R wp / R e = 1.39 by Rietveld analysis using powder neutron diffraction data. The basic (Ti 6 O 13 ) 2 − framework in H 2 Ti 6 O 13 was maintained nearly unchanged from that in the parent Li 2 Ti 6 O 13 . The hydrogen site in the tunnel space was refined with the strict O3 H1 distance of 0.94(1) A in H 2 Ti 6 O 13 . The structural stability of H 2 Ti 6 O 13 was confirmed by bond valence sums and 1 H-MAS NMR measurement. The total protonic conductivity in H 2 Ti 6 O 13 was estimated to be σ total = 8.32 × 10 − 6 S cm − 1 at room temperature from the results of AC-impedance measurements. This value is comparable to that of the well-known good protonic conducting ramsdellite-type H 2 Ti 3 O 7 .