Water Photooxidation by TiSi₂–TiO₂ Nanotubes

A composite photocatalyst comprised of self-assembled titania (TiO₂) nanotubes (NTs) coupled with titanium disilicide (TiSi₂) nanoparticles has been synthesized, characterized, and tested for photoelectrochemical hydrogen generation. The TiO₂ NT array is prepared by a sonoelectrochemical anodization method using ethylene glycol, ammonium fluoride, and disodium salt of ethylene diaminetetraacetic acid (Na₂[H₂EDTA]). TiSi₂ nanoparticles are produced from commercial bulk particles by a multiple ball milling followed by an ultrasonication process. The coupled catalyst is prepared by impregnating TiSi₂ nanoparticles into the TiO₂ nanotubes by multiple soaking processes, which leads to a noble structure with TiSi₂ nanorods inside the TiO₂ nanotubes. The heterostructural composite photoanode exhibited an enhanced photocurrent density of 3.49 mA/cm² at 0.2 V_Ag/Ag/Cl compared to TiO₂ nanotubes alone (0.9 mA/cm²) and can be considered as a potential possible candidate for the water splitting reaction using visible light. Pure TiSi₂ particles coated on ITO are also evaluated for the water splitting reaction, and it is found that TiSi₂ possesses good visible light activity (around 55% of the total activity). The combined light absorption (both UV and visible regions) of TiSi₂–TiO₂ NT material as evident from experimental results and the high charge transport properties of a self-assembled one-dimensional nanotube array make the composite potentially promising.