Effects of chloride and other anions on electrochemical chlorine evolution over self-doped TiO2 nanotube array

Electrochemically reduced TiO2 nanotube arrays (r-TiO2 NTA) have emerged as an alternative that can replace the dimensionally stable anode (DSA (R)) due to comparable performance for chlorine evolution reaction (ClER). However, previous studies have reported applications of r-TiO2 NTA for ClER only under limited conditions (concentrated NaCl solution without other anions). Thus, the potential of r-TiO2 NTA for CIER has not yet been fully demonstrated. Therefore, this study focused on investigating ClER of r-TiO2 NTA under various parameters such chloride concentration (5-1,000 mM) and the presence of other anions (i.e., SO4(2-), HPO4(2-), and CO3(2-)). The results suggest that, at low chloride concentration (5-50 mM NaCl), the r-TiO2 NTA exhibited higher performance for CIER (production rate of 3.35-9.82 mg l(-1) min(-1), current efficiency of 14.43-42.04%, energy consumption of 69.24-11.02 Wh g(Cl-2)(-1)) than RuO2 (2.55-7.88 mg l(-1) min(-1), 11.07-33.85% and 77.29-6.84 Wh g(Cl-2)(-1), respectively). Additionally, other anions did not affect the ClER of r-TiO2 NTA more than RuO2. These can be explained by the indirect pathway of ClER in r-TiO2 NTA while the direct pathway of RuO2 was negatively affected by dilute chloride and other anions.

Automated summary

Electrochemically reduced TiO2 nanotube arrays have shown promising performance in chlorine evolution reaction, particularly at low chloride concentrations, with minimal impact from other anions.