Influence of chromium content on microstructural and electrochemical supercapacitive properties of vanadium nitride thin films developed by reactive magnetron co-sputtering process

Two-dimensional nanostructured transition metal nitride-based thin film electrodes have been gaining importance in the electrochemical supercapacitor applications. In this work, Cr doped vanadium nitride (VN) thin films as an electrode material for high-performance supercapacitors have been demonstrated. In this study, reactive magnetron co-sputtering technique was adopted to fabricate phase pure VN as well as VN films doped with different Cr contents. These films were directly investigated as electrodes without using any additional binders. The phase purity and the surface chemistry of the Cr doped VN thin films were investigated using XRD and XPS techniques. Furthermore, EDS and X-ray elemental mappings were used to confirm the content of Cr and its distribution in these electrode films. The Cr ?5.7 at. % doped VN thin film electrodes exhibited an extraordinary supercapacitor performance with the maximum areal capacitance of 190 mF/cm² compared to the areal capacitance of 27 mF/cm² for the un-doped VN at a scan rate of 10 mV/s. Moreover, the Cr-5.7 at. % doped VN thin film electrodes showed excellent electrochemical cycling stability and excellent reversibility with the capacitance retention of 92.4 %. It could be noticed that the incorporation of metal such as Cr could be a viable method to improve the electronic or ionic conductivity of the metal nitrides for supercapacitor applications.