L. E. Walle

Heterogeneous reaction between Li and anatase TiO2 nanoparticles under ultra-high vacuum

We demonstrate heterogeneous chemistry between Li and anatase TiO2 nanoparticles under UHV. The reduction of TiO2 upon formation of lithium oxide proceeds via two different schemes: one that reduces Ti(4+) to Ti(3+) and one that reduces Ti(4+) directly to Ti(2+). The second scheme sets in only after a critical degree of reduction (i.e. Li amount) has been reached (Li/Ti = 0.28) and is associated with restructuring of the film. Two films with different morphologies were compared and the results demonstrate that the reaction between Li and larger TiO2 structures (30-50 nm) is kinetically restricted while such effects were significantly less prominent for small particles (10 nm).

Adsorption of methylamine on Ni3Al(111) and NiAl(110)-a high resolution photoelectron spectroscopy and density functional theory study

Methylamine adsorption on the ordered Ni(3)Al(111) and NiAl(110) surfaces has been investigated by high resolution photoelectron spectroscopy and density functional theory calculations. Methylamine adsorbs molecularly at both surfaces at low temperature (90 K). The experiments show that methylamine interacts with the surface aluminium atoms on both surfaces, resulting in a positive binding energy shift relative to the Al 2p bulk contributions. A shift towards lower binding energy is also observed on NiAl(110) attributed to first and second layer surface Al atoms not bonded to methylamine. According to total energy calculations methylamine binds through its N atom to Al on-top sites on NiAl(110) while the Ni on-top site is found to be slightly preferred over the Al on-top site on Ni(3)Al(111). Calculated adsorbate induced shifts are, however, in good agreement with the experimental values only when methylamine is situated in the Al on-top site on both surfaces. In both cases, a lone pair bonding mechanism is found.