Operando XAS and Electrocatalytic Properties of Transition Metal Oxynitride Thin Films

This study, supported by the DOE Visiting Faculty Program, investigates the electrocatalytic behavior of Group IVB transition-metal oxynitride (TMON) thin films for efficient water electrolysis. Focusing on the oxygen and hydrogen evolution reactions (OER/HER), TiOₓNᵧ thin films were fabricated at NCAT with controlled oxidation. Operando X-ray Absorption Spectroscopy (XAS) was employed to monitor oxidation-state changes and reactive intermediates under applied bias. Three major efforts included (1) development of thin-film samples, (2) electrochemical characterization to identify the most active films, and (3) in-situ XAS measurements. Preliminary Ti K-edge data reveal distinct Δμ(E) potential-dependent features indicating electron redistribution at the TiON–electrolyte interface. Spectral changes are correlated with electrochemical activity, elucidating the underlying charge-transfer and structural-evolution mechanisms.