Thin Titanium Nitride Layer-Inserted Porous Ru_0.3Sn_0.35Ti_0.35O_2–<i>x</i> Anode for Stable Chlorine Evolution Reaction

Developing robust anodes for the electrochemical chlorine evolution reaction (CER) is critical for producing chlorine, an essential commodity for various industries. Dimensionally stable anodes (DSAs), typically composed of Ti substrates and mixed metal oxide catalysts such as IrO2–RuO2–TiO2, are the current state-of-the-art for industrial CER anodes. To achieve high electrochemical stability of DSAs, designing catalytic systems based on an understanding of the failure mechanism is a crucial strategy. This study investigates the failure mechanisms of Ru0.3Sn0.35Ti0.35O2–x electrodes during CER under neutral conditions. Through combined cross-sectional scanning transmission electron microscopy (STEM)-electron energy loss spectroscopy (EELS) and electrochemical impedance spectroscopy (EIS) analyses, we identified that the primary failure mechanism is the passivation of the Ti substrate due to the formation and growth of a nonconductive TiOx layer at the interface. To mitigate this, we introduced a titanium nitride (TiN) interlayer, which transformed into a stable TiOxNy and TiO2 doped with NO2, preventing further oxidation of the Ti substrate and resulting in a more than 3-fold improvement in lifetime. We believe these findings provide valuable insights for designing highly durable anode structures for various electrochemical oxidation reactions.