Enhanced hardness and photocatalytic performance in anodic N-doped TiO2 layer on titanium using a non-aqueous nitrate electrolyte

An N-doped TiO2 layer with enhanced hardness and photocatalytic performance was fabricated on a titanium (Ti) substrate through anodization in a non-aqueous electrolyte comprising nitrate and glycerol, followed by heating at 723 K in air. Glycerol as an electrolyte solvent formed a homogeneous and dense oxide layer and resulted in improved layer hardness. The fabricated layer comprised rutile and anatase TiO2 with ~1 at% of nitrogen doping. Visible-light responsive photocatalytic activity was enhanced with increasing nitrate concentration in the electrolyte, as this optimized the anatase/rutile TiO2 ratio of the layer. The fabricated TiO2 layer showed excellent antibacterial activity that was superior to a commercially available photocatalytic TiO2 layer, demonstrating that the proposed treatment process is capable of fabricating surface modified Ti biomaterial. •Anodization of Ti in a non-aqueous nitrate electrolyte formed a N-doped TiO2 layer.•Glycerol as an electrolyte solvent significantly enhanced layer toughness.•Increasing nitrate concentration in electrolyte improved photocatalytic activity.•The enhanced activity is caused by optimization of the crystal structure.•The anodic TiO2 showed antibacterial activity possibly applicable to biomaterials.