Modification of Porous Titania Templates for Uniform Metal Electrodeposition from Deep Eutectic Solvent

Abstract

Zinc electrochemical deposition in porous anodic titania from 0.5 M ZnCl2 solution in choline chloride based deep eutectic solvent is reported. Electroreduction is performed by a pulse method in titanium dioxide templates modified in three different ways. Titania nanotubes were formed in ethylene glycol based electrolyte with 0,38% (wt) ammonium fluoride and 1,79% (wt) of water. The first template has been used as-prepared, without any modification. Such a matrix shows a low fill-factor and zinc electrodeposition mainly occurs on the top of the tubes. The next template was annealed at 450°C to complete crystallization of titania. It results in electrodeposition of zinc along the entire tube surface and consequently in formation of coaxial structure. The third template was modified based on selective crystallization of the pore bottoms using higher anodization voltage (80 V) than the one used for tubes formation (40 V) in sulfuric acid electrolyte. The successful bottom-up filling of the titania nanotubes is demonstrated in this case. Investigation of the tubes filling is performed by a set of complementary techniques such as GDOES, SEM and TEM.