Capacitive and Oxidant Generating Properties of Black-Colored TiO2 Nanotube Array Fabricated by Electrochemical Self-Doping

Recently, black-colored TiO2 NTA (denoted as black TiO2 NTA) fabricated by self-doping of TiO2 NTA with the amorphous phase led to significant success as a visible-light-active photocatalyst. This enhanced photocatalytic activity is largely attributed to a higher charge carrier density as an effect of electrochemical self-doping resulting in a higher optical absorbance and lower transport resistance. Nevertheless, the potential of black TiO2 NTA for other electrochemical applications, such as a supercapacitor and an oxidant-generating anode, has not been fully investigated. Here, we report the capacitive and oxidant generating properties of black TiO2 NTA. The black TiO2 NTA exhibited significantly a high value for areal capacitance with a good rate capability and novel electrocatalytic activity in generating (center dot)OHs and Cl-2 compared to pristine TiO2 NTA with the anatase phase. This study suggests that the black TiO2 NTA be applied as a supercapacitor and an oxidant generating anode.