Transition metal (Zn, Mn, and Ni) incorporated CuO nanostructures for supercapacitor applications

Abstract

Striking features of cost-effectiveness, eco-friendliness, abundant resources, facile fabrication, and primarily, the high theoretical capacitance of CuO have established it as a smart choice for electrodes in pseudocapacitors, yet its practical utilization is hindered by its low electrical conductivity. Considering this, herein, we have made an effort to improve its conductivity by doping it with various transition metals and investigating each sample's electrochemical performance. Fabrication of pure and TM-doped CuO NPs (Cu1-xTMxO, where TM = Zn, Mn, Ni, and x = 0.05) has been carried out via the coprecipitation method, followed by calcination. The X-ray diffraction technique confirms the monoclinic structure of all the samples. Nanoplate, nanoflake, and nano rod-like morphology are exhibited by CuO, Zn-doped CuO, and Mn-doped CuO, respectively. The maximum value of the surface area is noted for Cu0.95Ni0.05O in BET analysis. Whereas, uniformly distributed arbitrarily shaped nano-particles are observed for Ni-doped CuO. The analysis of electrochemical performance reveals that at 5 mVs−1, 153, 109, 77, and 507 Fg−1 of specific capacitance has been delivered by CuO, Cu0.95Zn0.05O, Cu0.95Mn0.05O, and Cu0.95Ni0.05O, respectively. Ni-doped CuO showed outstanding specific capacitance which is threefold better than pristine CuO. Moreover, it also demonstrated the best cyclic stability with a retained capacitance of 93 % by the end of 2000 cycles, along with the lowest charge transfer and solution resistance amongst all as-prepared samples. Its extraordinary performance is a consequence of its uniformly distributed highly porous morphology and better electrical conductivity. Hence, this study suggests Ni-doped CuO be the most desirable electrode material for pseudocapacitors.