Electrochemical, top-down nanostructured pseudocapacitive electrodes for enhanced specific capacitance and cycling efficiencyElectronic supplementary information (ESI) available. See DOI: 10.1039/c7nr08164b

• Main Authors: Kalyani, Vishwanath, Mondal, Sudeshna, Saha, Jayeeta, Subramaniam, Chandramouli
• Format: Article
• Language: English
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/c7nr08164b

Stabilization of the electroactive redox centers on ideally polarisable conductive electrodes is a critical challenge for realizing stable, high performing pseudocapacitive energy storage devices. Here, we report a top-down, electrochemical nanostructuring route based on voltammetric cycling to stabilize β-MnO 2 on a single walled carbon nanotube (CNT) scaffold from a MnMoO 4 precursor. Such in situ nanostructuring results in controlled disintegration of an ∼8 μm almond like structure to form ∼29 nm β-MnO 2 resulting in a 59% increase in the specific surface area and a 31% increase in the porosity of the pseudocapacitive electrode. Consequently, the specific capacitance and areal capacitance increase by ∼75% and ∼40%, respectively. Such controlled, top-down nanostructuring is confirmed through binding energy changes to Mo 3d, C 1s, O 1s and Mn 2p respectively in XPS. Furthermore, Raman spectral mapping confirms the sequential nanostructuring initiating from the interface of CNTs with MnMoO 4 and proceeding outwards. Thus, the process yields the final CNT/β-MnO 2 electrode that is electrically conductive, facilitates rapid charge transfer, and has increased capacitance and longer stability. Furthermore, the charge-transfer resistance and equivalent resistance are significantly lower compared to conventional activated carbon based electrodes. Electrochemical nanostructuring of MnMoO 4 to β-MnO 2 on a CNT-scaffold is demonstrated to realize psuedocapacitors with high energy density, power density and lifetime.