Plasma spraying of efficient photoactive TiO2 coatings

In TiO2 coatings for photocatalytic applications or dye-sensitized solar cells, anatase phase with specific rutile content is often preferred to achieve optimum activity. At appropriate process parameters, such phase composition can be obtained by suspension plasma spraying (SPS). However, immediately after deposition, partial transformation to rutile can take place if the substrate temperature is sufficient. Experimental results show that the phase composition has to be balanced with other coating characteristics like microstructure and deposition rate.Another approach to improve the photoactivity of TiO2 is nitrogen doping. It is known that such anionic dopant can create states within the band gap so as to reduce locally the energy barrier of the photoexited electron. Thus, the photoactivity in the range of visible light can be enhanced. TiN addition was investigated to introduce nitrogen in TiO2 coatings directly during SPS. First results are presented.

► Nitrogen-doped TiO2 coatings by suspension plasma spraying adding TiN to feedstock.
► Due to high substrate temperatures, anatase is predominantly transformed to rutile.
► First indications on enhanced the photoactivity by PSD absorbance measurements.