Résumé
Here we investigated the electrochemical performance of molybdenum nitride films as an efficient electrode for asymmetric micro-supercapacitors. Molybdenum nitride films were successfully deposited and optimized by reactive magnetron sputtering. On the one hand, the tuning of several deposition parameters (pressure, gas flow rates) allows obtaining molybdenum nitride electrode with high porosity and high electrical conductivity. On the other hand, Operando X-ray diffraction, operando Raman spectroscopy and operando X-ray absorption spectroscopy are combined to unveil the charge storage process in 1 M KOH aqueous electrolyte. These measurements clearly reveal the role of molybdenum oxide species in the pseudocapacitive mechanism at the oxide/electrolyte interface. High volumetric capacitance up to 624 F·cm⁻³ with excellent capacitance retention of 95 % over 20 000 cycles was achieved in 1 M KOH.