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 (•)OHs and Cl2 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.