Annual Report 2012 - Latvijas Universitātes Cietvielu fizikas institūts

Titania with anatase structure is investigated due to its photo-active properties that can
be used in the water photocatalysis applications and in the organic photovoltaic devices
(L.Grinberga et all, 2012). In this work the anodization conditions are described to
obtain stable thin film TiO layers formed from vertically oriented nanotubes with
approximate height 358 nm, inner tube diameter 48 nm and wall thickness 20 nm, but
centre to centre distance 100 nm. Annealed at 500 o C TiO 2 layer mostly consists from
oxide with anatase structure, though XRD spectroscopy shows rutile impurities as well.
Obtained nanotube layers are sensitive mostly to UV light.
Hydrogen storage: Natural clinoptilolite is activated with palladium and tested for
hydrogen adsorption capability at room temperatures (Lesnicenoks et all, 2012). Simple
method is developed to measure hydrogen storage capability in solid materials with a
commercial thermogravimeter. This method consists of two stages: material cleaning
stage in inert gas (argon, nitrogen) flow, and hydrogen sorption stage where measured
sample is cooled down from elevated to room temperature at hydrogen atmosphere. It is
found that samples of finely grounded zeolite showed higher hydrogen adsorption
capacity – up to 7 wt%.
Slightly lower adsorption capability is observed for finely and course grounded zeolite
samples that was activated with Pd.-. Hypothesis that the heating of zeolite in argon
atmosphere activates the pore structure in zeolite material, where hydrogen
encapsulation (trapping) can occur when cooling down to room temperature is proposed.
An effect of catalyst (Pt) on hydrogen sorption capability is explained by spillover
phenomena were less-porous fractions of natural clinoptilolite sample (quartz and
muscovite) are involved in hydrogen transport.
Proton conducting membrane research: All studied composite Nafion 112
membranes impregnated with different hydroxyl ammonium ionic liquids showed
similar behavior (V.Garaev et all, 2012). The conductivity decrease was not observed in
a temperature range from 30 o C to 90 o C in ambient environment due to the potential
water loss. Almost all composites have higher ion conductivity than a pure Nafion 112
at 90 o C. All ionic liquids increased the thermal stability of Nafion membrane
approximately by 50 o C. The composite membrane of Nafion with ionic liquids has
potential to be used in ionic devices at increased temperatures, especially acetates.
However, the conductivity in a temperature range over 90 o C also should be studied. At
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