Molybdenum substituted Ni-Mn cobaltite spinel nanostructure for high performance Ultracapacitors

Abstract

The role of electrode materials is crucial in high-capacity and high-power-density storage devices like supercapacitors because they offer superior electrochemical characteristics. The current study employs a hydrothermal approach to synthesize Molybdenum (Mo) doped spinel cobaltite nanostructure Mn_0.5Ni_0.5Mo_xCo_2-2xO₄ (Mn–Ni/Mo) where (x = 0.00, 0.02,0.04 and 0.06). Additionally, the chemical and physical characteristics of the synthesized nanostructures, were assessed using XPS, XRD, BET, TEM, SEM, and EDX methods. Further, investigation about the electrochemical evaluation of novel nanostructures as an active electrode material was conducted in 1 M Na₂SO₄, employing two-electrode system in asymmetric configuration. Investigations using different electrochemical characterization techniques of CV, EIS and GCD showed the notable effect of Mo on the overall electrochemical characteristics. In comparison to different doping ratio, the sample with 2 % doping of Mo showed the better performance in terms of bulk resistance (∼1 Ω), phase angle (∼67°) and response time (∼20 s). The optimum doping ratio (x = 0.02) also showed the capacitance retention of more than 45 % at a scan rate of 100 mV s⁻¹. Further, at a current load of 0.5 A g⁻¹, the optimum dopant demonstrated an outstanding specific capacitance of 184.9F g⁻¹ and a stability of more than 88 % even after 10,000 GCD cycles. Moreover, the optimized electrode revealed noteworthy specific energy of 6.42 Wh Kg^{- 1} at a specific power of 3.91 kW kg⁻¹. These findings exhibit a great promise for the prepared nanostructure in energy storage devices.