High chlorine evolution performance of electrochemically reduced TiO2 nanotube array coated with a thin RuO2 layer by the self-synthetic method

Abstract

Recently, reduced TiO₂ nanotube arrays via electrochemical self-doping (r-TiO₂) 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-TiO₂ with a thin RuO₂ layer coating on the nanotube structure (RuO₂@r-TiO₂). The RuO₂ thin layer was successfully coated on the surface of r-TiO₂. This was accomplished with a self-synthesized layer of ruthenium precursor originating from a spontaneous redox reaction between Ti³⁺ and metal ions on the r-TiO₂ surface and thermal treatment. The thickness of the thin RuO₂ layer was approximately 30 nm on the nanotube surface of RuO₂@r-TiO₂ without severe pore blocking. In chlorine production, RuO₂@r-TiO₂ exhibited higher current efficiency (∼81.0%) and lower energy consumption (∼3.0 W h g⁻¹) than the r-TiO₂ (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 RuO₂@r-TiO₂ compared with r-TiO₂ (ca. 1.2 h). The results suggest a new route to provide a thin layer coating on r-TiO₂ and to synthesize a high performance oxidant-generating anode.