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Recently, transition-metal-based hydroxide materials have attracted significant attention in various electrochemical applications owing to their low cost, high stability, and versatility in composition and morphology. Among these applications, transition-metal-based hydroxides have exhibited significant potential in supercapacitors owing to their multiple redox states that can considerably enhance the supercapacitance performance. In this study, nanostructured Ni-Mn double hydroxide is directly grown on a conductive substrate using an electrodeposition method. Ni-Mn double hydroxide exhibits excellent electrochemical charge-storage properties in a 1 M KOH electrolyte, such as a specific capacitance of 1364 Fg-1 at a current density of 1 mAcm-2 and a capacitance retention of 94% over 3000 charge-discharge cycles at a current density of 10 mAcm-2. The present work demonstrates a scalable, time-saving, and cost-effective approach for the preparation of Ni-Mn double hydroxide with potential application in high-charge-storage kinetics, which can also be extended for other transition-metal-based double hydroxides.

MnCo2S4/CoS2 electrode with highly accessible electroactive sites is prepared using the hydrothermal method. The electrode exhibits an areal capacitance of 0.75 Fcm-2 at 6 mAcm-2 in 1 M KOH. The capacitance is further increased to 2.06 Fcm-2 by adding K3Fe(CN)6 and K4Fe(CN)6 (a redox couple) to KOH. This increment is associated with the redox-active properties of cobalt and manganese transition metals, as well as the ion pair of [Fe(CN)6]-3/[Fe(CN)6]-4. The capacitance retention of the MnCo2S4/CoS2 electrode is 87.5% for successive 4000 charge-discharge cycles at 10 mAcm-2 in a composite electrolyte system of KOH and ferri/ferrocyanide. The capacitance enhancement is supported by the lowest equivalent series resistance (0.62 Ωcm-2) of MnCo2S4/CoS2 in the presence of redox additive couple compared with the bare KOH electrolyte.

Today smartphones are readily available with source of power, faster processing capabilities and connectivity. In this paper, we propose design of circuit to harvest power from widely available standard 3.5mm headphone jack of smartphone itself. Headphone jack can generate tones (sine or square) within the frequency range of 20–20KHz. we have also developed GUI of an android application for tone generation which plays sine wave. The audio output channels of smartphones from different manufacturers were characterized in order to determine the range of design parameters. Proposed design provides few milliwatts to power mHealth peripherals and enhances practicality of smartphone as a medical device. It could be the better option for battery dependent devices. Headphone jack interface could be used to develop modular platforms to monitor vital signs such as Pulse rate, SpO2, EKG.