Thin Titanium Nitride\nLayer-Inserted Porous Ru<sub>0.3</sub>Sn<sub>0.35</sub>Ti<sub>0.35</sub>O<sub>2–<i>x</i></sub> Anode for Stable Chlorine\nEvolution Reaction

Developing robust anodes for the electrochemical chlorine\nevolution\nreaction (CER) is critical for producing chlorine, an essential commodity\nfor various industries. Dimensionally stable anodes (DSAs), typically\ncomposed of Ti substrates and mixed metal oxide catalysts such as\nIrO<sub>2</sub>–RuO<sub>2</sub>–TiO<sub>2</sub>, are\nthe current state-of-the-art for industrial CER anodes. To achieve\nhigh electrochemical stability of DSAs, designing catalytic systems\nbased on an understanding of the failure mechanism is a crucial strategy.\nThis study investigates the failure mechanisms of Ru<sub>0.3</sub>Sn<sub>0.35</sub>Ti<sub>0.35</sub>O<sub>2–<i>x</i></sub> electrodes during CER under neutral conditions. Through combined\ncross-sectional scanning transmission electron microscopy (STEM)-electron\nenergy loss spectroscopy (EELS) and electrochemical impedance spectroscopy\n(EIS) analyses, we identified that the primary failure mechanism is\nthe passivation of the Ti substrate due to the formation and growth\nof a nonconductive TiO<sub><i>x</i></sub> layer at the interface.\nTo mitigate this, we introduced a titanium nitride (TiN) interlayer,\nwhich transformed into a stable TiO<sub><i>x</i></sub>N<sub><i>y</i></sub> and TiO<sub>2</sub> doped with NO<sub>2</sub>, preventing further oxidation of the Ti substrate and resulting\nin a more than 3-fold improvement in lifetime. We believe these findings\nprovide valuable insights for designing highly durable anode structures\nfor various electrochemical oxidation reactions.