Elucidating Mn<sup>2+</sup>/Mn<sup>3+</sup> and Ni<sup>0</sup>/Ni<sup>2+</sup> Redox Synergy in Hair-Derived Carbon-Supported Ag/Ni–MnO<sub><i>x</i></sub> Supercapacitor
Abdulkadeem Sanni, Durai Govindarajan, Wathanyu Kao‐ian, Wanwisa Limphirat, Mongkol Tipplook, Katsuya Teshima, Jayaraman Theerthagiri, Myong Yong Choi, Soorathep Kheawhom
Abstract
High Resolution Image Download MS PowerPoint Slide Despite their critical importance, developing sustainable high-performance supercapacitor (SC) electrodes with long-term stability poses significant challenges. Herein, we report a novel ternary composite electrode in which Ag/Ni-doped manganese oxide (Ag/NiO x @Mn y O z ) is supported on human hair-derived activated carbon (HHC). This composite is synthesized via a one-pot hydrothermal process followed by thermal annealing at 800 °C, a strategy that creates a conductive Ag/Ni bimetallic network and abundant oxygen vacancies in the NiO x and Mn y O z phases. During operation, operando X-ray absorption spectroscopy (XAS) confirms reversible dual-ion redox transitions (Mn 2+ /Mn 3+ and Ni 0 /Ni 2+ ) in the cathode, highlighting the material’s enhanced redox activity. As a result, HHC-supported Ag/NiO x @Mn y O z exhibits an exceptional specific capacitance (Cs) of 1770 F g –1 at 5 mV s –1 in three-electrode tests. When assembled into an asymmetric hybrid supercapacitor (AHSC), the device delivers a high energy density of 37.53 Wh kg –1 and a power density of 2251.8 W kg –1 at 3 A g –1 while retaining ∼82% of its initial capacitance after 5000 charge–discharge cycles. These results confirm the effectiveness of our sustainable HHC-supported Ag/NiO x @Mn y O z framework in addressing the enduring trade-off between energy density, power density, and cycling stability in next-generation SCs.