Pseudocapacitive Titanium Oxynitride Nanowires by Pulsed-Laser Deposition for Ultra-High Capacitance Supercapacitors

Titanium-based metal oxynitrides, TiN_xO_y (TiNO), are promising materials for energy conversion and storage. Rocksalt TiNO films, synthesized in-situ using pulsed laser deposition and a varied oxygen partial pressure, were recently found to exhibit high electrochemical performance, with overpotentials for water oxidation that can be as low as 290 mV at 10 mA/cm² [1]. It has also been shown that the bandgaps of TiNO films can be optimized for solar-to-hydrogen conversion by modulating the nitrogen-to-oxygen content [2]. In this presentation, we report the synthesis and electrochemical performance of multifunctional 2-dimensional (2D) TiNO thin films and 1-dimensional (1D) TiNO nanowires for electrochemical energy storage. The synthesis uses a binder-free, non-clean room-specific pulsed laser deposition method which enables to achieve nanowires with excellent crystallinity and high chemical homogeneity. The cyclic voltammetry measurements show that the specific capacitances of the TiNO nanowires (2,725 mF.cm-2) are nearly six times more than those of the TiNO thin films (400 mF.cm-2). These high specific capacitances are on par with the highest values reported for the recently top-tier nanoscale electrode materials. First-principles simulations suggest that they originate from the high concentration of surface-active sites on TiNO materials, combined with the higher effective surface area of nanowires.