Structure of the amorphous titania precursor phase of N-doped photocatalysts.

ABSTRACT: Amorphous titania samples prepared by ammonia solution neutralization of titanyl sulphate have been characterized by chemical and thermal analyses, and with reciprocal-space and real-space fitting of wide-angle synchrotron X-ray scattering data. A model that fits both the chemical and structural data comprises small segments of lepidocrocite-type layer that are offset by corner-sharing as in the monoclinic titanic acids H₂Ti _n O_2n+1·mH₂O. The amorphous phase composition that best fits the combined chemical and scattering data is [(NH₄)₃H₂₁Ti₂₀O₅₂]·14H₂O, where the formula within the brackets is the cluster composition and the H₂O outside the brackets is physically adsorbed. The NH₄ ⁺ cations are an integral part of the clusters and are bonded to layer anions at the corners of the offset layers, as occurs in the alkali metal stepped-layer titanates. The stepped-layer model is shown to give a consistent mechanism for the reaction of aqueous ammonia with solid hydrated titanyl sulphate, in which the amorphous product retains the exact size and shape of the reacting titanyl sulphate crystals.

SUBMITTER: Grey IE 

PROVIDER: S-EPMC8695186 | biostudies-literature | 2021 Feb

REPOSITORIES: biostudies-literature