Tuning the electrochemical potential window of Niobium carbide based electrodes for symmetric electrochemical supercapacitors

The electrochemical potential window for nano-sized Niobium carbide (NbC) based electrodes for supercapacitive energy storage applications was investigated. The nano-size NbC electrodes were fabricated and supported on carbon cloth (CC). The NbC@CC materials were assembled into a symmetric supercapacitor with a 1 M sulfuric acid (H₂SO₄) as an electrolyte. The properties of the symmetric supercapacitor were evaluated for their electrochemical behavior, surface properties and morphology. The results showed that the nano-size NbC material was uniformly coated on the surface of CC. The electrochemical performance of the fabricated symmetric supercapacitor was evaluated in the range from -2V to + 2V and showed that the currents were spiked. To further understand the electrochemical behavior, the potentials were systematically reduced to +0.8V and evaluated. The charging-discharging behavior was studied systematically with the aim of avoiding the overestimation of the electrode performance. The specific capacitance was estimated to be around 27 F/g at the reduced potential window. Overall, this work presents a selection of the right potential window for the testing of the NbC based supercapacitor in such a way that avoids the overestimation of the potential window.