Properties of hydrated TiO2 and SiO2 nanoclusters: dependence on size, temperature and water vapour pressure. Issue 45 (14th November 2018) - Cuko, Andi
Abstract : The stabilities and properties of globally optimised (TiO2 ) M (H2 O) N and (SiO2 ) M (H2 O) N clusters with M = 4–16 and a range of N / M ratios are studied with respect temperature and water vapour pressure. Our systematic study provides a comparative reference for understanding hydration of nano-silica and nano-titania. Abstract : Nanoscale titania (TiO2 ) and silica (SiO2 ) are massively produced technologically important nanomaterials used in a wide range of technological applications where nano-titania is the active component ( e.g. water splitting, pollution remediation, self-cleaning coatings). Generally, these applications entail contact with water and a degree of hydration of these nano-oxides. Although the hydration of nano-silica has been fairly well studied, the corresponding level of microscopic understanding for nano-titania is severely lacking. Here, using accurate electronic structure calculations we perform a detailed and comprehensive study of the hydration of titania nanoclusters. Firstly, using global optimisation, we establish the most energetically stable structures of a set of (TiO2 ) M (H2 O) N nanoclusters with sizes ranging through M = 4–16 and with N / M ratios of ≤ 1.0. Using this extensive dataset we investigate how the structures, energy gaps, and thermodynamic stabilities of these species depend on size, temperature and water vapour pressure. To provide a broader chemical context for our study we also provide this full set of data for the respective set of (SiO2 ) M (H2 O) N nanoclusters which we use to compare and contrast their properties with those of nano-titania. Our broad systematic study thus provides a comparative and foundational reference study for a thorough understanding of how hydration affects the structure, energetics and properties of both nano-SiO2 and nano-TiO2 .