Microwave-tuned Mn-doped ZnO for all-in-one supercapacitors: correlating defect chemistry with electrochemical behavior

Official URL: https://dx.doi.org/10.1016/j.jcis.2025.138012

Zinc oxide-based (ZnO) electrode materials have emerged as contenders for heightened cost efficiency, fast charge-discharge prowess, outstanding performance metrics, and remarkable cycle stability in supercapacitor technologies. Among the myriad synthesis techniques, the microwave-assisted approach distinguishes itself with an array of advantages, being time-efficient, eco-friendly, and adept at providing accurate control over the complex ZnO morphology. Introducing ions like [Figure presented] into the ZnO lattice further propels the electrochemical performance of supercapacitors into superior territories. Hence, this investigation meticulously prepared a series of undoped and Mn-doped ZnO materials utilizing a microwave-assisted synthesis method across four different microwave powers ranging from 160 to 800 W. Cutting-edge morpho-structural characterization techniques, including X-ray diffraction, scanning electron microscopy, electron paramagnetic resonance, photoluminescence, and Raman spectroscopy, were employed to delve into the structure and defect centers of the ZnO-based samples. It has been conclusively demonstrated that the concentration of [Figure presented] is pivotal, offering additional charge carriers without compromising the crystallinity of ZnO while also enhancing diffusion correlated with Faradaic redox reactions—thereby escalating the supercapacitor's properties. A doping concentration of 2% Mn-ions balances charge carriers with structural integrity. This sample achieved a specific capacitance of 340 F/g, a power density of 59.7 kW/kg, and an energy density of 47.1 Wh/kg. Across the board, all samples demonstrate impressive stability, retaining over 70% capacity after 5000 charge-discharge cycles. Notably, ZnO with 2% Mn synthesized at 160 W excels with over 90% capacitance retention. This distinct behavior is attributed to the transformative influence of Mn ion doping on ZnO's structural and morphological attributes.