Solar photocatalytic activity of nitrogen doped TiO₂ coating by micro-arc oxidation

ABSTRACT

Nitrogen doped porous TiO₂ (N-TiO₂) coating was developed from titanium nitride (TiN) by micro-arc oxidation (MAO), whereas TiN was prepared by plasma nitriding on commercially pure (Cp) titanium. The surface roughness of the N-TiO₂ coating was greater than that of the TiO₂ coating due to different MAO processing parameters. The band gap energy of N-TiO₂ coating was reduced to 2.92 eV compared to TiO₂ coating. The band gap energy reduction of N-TiO₂ was attributed to nitrogen doping and the mixture of anatase, rutile and new phase (TiN_0.30). The photoluminescence study demonstrated that the recombination rate of photo-generated electron–hole pairs of TiO₂ was significantly suppressed after doping with nitrogen. N-TiO₂ exhibited higher photocatalytic activity towards methylene blue dye degradation than to pure TiO₂ coating. The recyclability test of N-TiO₂ coating showed constant photocatalytic efficiency after the fourth run. Hence, N-TiO₂ porous coating could be a promising material for immobilised solar photocatalytic applications.

KEYWORDS:

• Plasma nitriding
• MAO
• N-TiO₂
• Anatase
• Rutile
• Photocatalytic activity