Investigating into the intricacies of charge storage kinetics in NbMn-oxide composite electrodes for asymmetric supercapacitor and HER applications
Journal of Alloys and Compounds(2023)
摘要
In this paper, we present an effortless hydrothermal method for depositing niobium and manganese composite oxides onto Ni-foam. The formation of the desired NbMn-oxide phase is confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analytical tools. In the study, we systematically investigated the effect of varying Mn concentrations on the physicochemical properties and energy storage performance of the NbMn-oxide composite. The NbMn-oxide exhibited nanoplates assembled from sphere-shaped structures along with irregularly shaped rectangular blocks of nano/micro-structures, forming a porous framework. The electrode with an Mn concentration of 0.02 M displayed an areal capacitance of approximately 5987.8 mF/cm2 and an energy density of 0.13 mWh/cm2, even at a high current density of 10 mA/cm2. Additionally, the hydrogen evolution reaction (HER) performance of the NbMn-oxide composite electrode was evaluated and it exhibited an overpotential of 86 mV to achieve a current density of 10 mA/cm². The electrode also displayed stable performance for approximately 7 h, with only a slight increase in overpotential from − 0.218 to − 0.263 V against the reversible hydrogen electrode (RHE) during the stability test. The investigation of charge storage kinetics revealed the dominance of the diffusion process over the capacitive process, with the quasi-reversible redox reactions in the composite metal-oxides responsible for the high electrochemical performance. The assembled asymmetric supercapacitor device, utilizing NbMn-2 (positive) and activated carbon (negative) electrodes, demonstrated an impressive energy density of 0.20 mWh/cm2 at a power density of 3.75 mW/cm2, coupled with exceptional cyclability (97%). These findings highlight the potential of Nb-based composite electrodes for both supercapacitor and HER water-splitting applications and underscore their significant potential for electrochemical energy conversion and storage.
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关键词
asymmetric supercapacitor,charge storage kinetics,composite electrodes,nbmn-oxide
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