Titanium Nitride Films as Durable, Enhancing Windows for Electrochemical Infrared Spectroscopy

As electrochemical reactions become more central to the green energy transition, spectroscopic means to characterize these reactions are becoming more valuable. Electrochemical attenuated total reflectance - surface enhanced infrared spectroscopy (ATR-SEIRAS) is of particular note for its ability to characterize molecules at the catalyst-electrolyte interface. However, extensive studies using electrochemical ATR-SEIRAS are limited by the poor chemical and mechanical stability or optical properties of window materials. In this work, we report titanium nitride (TiN) prepared in a single-step reactive sputtering process with Ar and N₂ plasma as a new material for ATR-SEIRAS on account of its ease of preparation, good conductivity, outstanding mechanical and chemical stability, and ability to acquire surface-enhanced spectra. After depositing Pt on the TiN surface, a CO probe is used to demonstrate the spectroscopic utility of the TiN layers. TiN also shows remarkable chemical stability in the same strong alkaline (1 M KOH) and acidic (0.5 M H₂SO₄) conditions often used for energy-related studies, especially in comparison to the classic electroless deposited Au system typically utilized. Finally, we validate TiN for studying energy-relevant reactions, demonstrating that meaningful spectra can be collected in CO₂ reduction and O₂ evolution. These properties make TiN one of the most promising optical window materials yet reported for electrochemical ATR-SEIRAS.