Sputter-Deposited Binder-Free Nanopyramidal Cr/γ-Mo₂N TFEs for High-Performance Supercapacitors

Due to their outstanding power density, long cycle life and low cost, supercapacitors have gained much interest. As for supercapacitor electrodes, molybdenum nitrides show promising potential. Molybdenum nitrides, however, are mainly prepared as nanopowders via a chemical route and require binders for the manufacture of electrodes. Such electrodes can impair the performance of supercapacitors. Herein, binder-free chromium (Cr)-doped molybdenum nitride (Mo₂N) TFEs having different Cr concentrations are prepared via a reactive co-sputtering technique. The Cr-doped Mo₂N films prepared have a cubic phase structure of γ-Mo₂N with a minor shift in the (111) plane. While un-doped Mo₂N films exhibit a spherical morphology, Cr-doped Mo₂N films demonstrate a clear pyramid-like surface morphology. The developed Cr-doped Mo₂N films contain 0-7.9 at.% of Cr in Mo₂N lattice. A supercapacitor using a Cr-doped Mo₂N electrode having the highest concentration of Cr reveals maximum areal capacity of 2780 mC/cm², which is much higher than that of an un-doped Mo₂N electrode (110 mC/cm²). Furthermore, the Cr-doped Mo₂N electrode demonstrates excellent cycling stability, achieving ~ 94.6% capacity retention for about 2000 cycles. The reactive co-sputtering proves to be a suitable technique for fabrication of binder-free TFEs for high-performance energy storage device applications.