High chlorine evolution performance of electrochemically reduced TiO 2 nanotube array coated with a thin RuO 2 layer by the self-synthetic method.

Recently, reduced TiO 2 nanotube arrays via electrochemical self-doping (r-TiO 2 ) are emerging as a good alternative to conventional dimensionally stable anodes (DSAs) due to their comparable performance and low-cost. However, compared with conventional DSAs, they suffer from poor stability, low current efficiency, and high energy consumption. Therefore, this study aims to advance the electrochemical performances in the chlorine evolution of r-TiO 2 with a thin RuO 2 layer coating on the nanotube structure (RuO 2 @r-TiO 2 ). The RuO 2 thin layer was successfully coated on the surface of r-TiO 2 . This was accomplished with a self-synthesized layer of ruthenium precursor originating from a spontaneous redox reaction between Ti 3+ and metal ions on the r-TiO 2 surface and thermal treatment. The thickness of the thin RuO 2 layer was approximately 30 nm on the nanotube surface of RuO 2 @r-TiO 2 without severe pore blocking. In chlorine production, RuO 2 @r-TiO 2 exhibited higher current efficiency (∼81.0%) and lower energy consumption (∼3.0 W h g -1 ) than the r-TiO 2 (current efficiency of ∼64.7% of and energy consumption of ∼5.2 W h g -1 ). In addition, the stability ( ca. 22 h) was around 20-fold enhancement in RuO 2 @r-TiO 2 compared with r-TiO 2 ( ca. 1.2 h). The results suggest a new route to provide a thin layer coating on r-TiO 2 and to synthesize a high performance oxidant-generating anode.