Energetics of nanocrystalline TiO2

M R Ranade; A Navrotsky; H Z Zhang; J F Banfield; S H Elder; A Zaban; P H Borse; S K Kulkarni; G S Doran; H J Whitfield

doi:10.1073/pnas.251534898

Energetics of nanocrystalline TiO2

Proc Natl Acad Sci U S A. 2002 Apr 30;99 Suppl 2(Suppl 2):6476-81. doi: 10.1073/pnas.251534898. Epub 2002 Mar 5.

Authors

M R Ranade¹, A Navrotsky, H Z Zhang, J F Banfield, S H Elder, A Zaban, P H Borse, S K Kulkarni, G S Doran, H J Whitfield

Affiliation

¹ University of California, Department of Chemical Engineering and Materials Science, Thermochemistry Facility, Davis, CA 95616, USA.

Abstract

The energetics of the TiO(2) polymorphs (rutile, anatase, and brookite) were studied by high temperature oxide melt drop solution calorimetry. Relative to bulk rutile, bulk brookite is 0.71 +/- 0.38 kJ/mol (6) and bulk anatase is 2.61 +/- 0.41 kJ/mol higher in enthalpy. The surface enthalpies of rutile, brookite, and anatase are 2.2 +/- 0.2 J/m(2), 1.0 +/- 0.2 J/m(2), and 0.4 +/- 0.1 J/m(2), respectively. The closely balanced energetics directly confirm the crossover in stability of nanophase polymorphs inferred by Zhang and Banfield (7). An amorphous sample with surface area of 34,600 m(2)/mol is 24.25 +/- 0.88 kJ/mol higher in enthalpy than bulk rutile.