No abstract

Direct carbonisation of conjugated microporous polymers (CMPs) yields porosity-engineered carbons, opening up a new source of electroactive materials.

Manganese oxides can undergo an electrochemical activation step that leads to greater capacitances, of which the structural change and mechanism remains poorly understood. Herein we present a wideranging study on a manganese oxide synthesised by annealing manganese(II) acetate precursor to 300 C, which includes in operando monitoring of the structural evolution during the activation process via in situ Raman microscopy. Based on powder X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron and ex situ Raman microscopy, the as prepared manganese oxide was characterised as hausmannite-Mn 3 O 4 with a minor portion of MnO 2 . The activation process of converting as-prepared hausmannite-Mn 3 O 4 into amorphous MnO 2 (with localised birnessite structure) by electrochemical cycling in 0.5 M Na 2 SO 4 was examined. After activation, the activated MnO x exhibited capacitive performance of 174 F g À1 at a mass loading of 0.71 mg cm À2 . The charge storage mechanism is proposed as the redox reaction between Mn(III) and Mn(IV) at outer surface active sites, since the disordered birnessite-MnO 2 does not provide an ordered layer structure for cations and/or protons to intercalate. † Electronic supplementary information (ESI) available: Literature comparison, potential of quasi reference electrode measurement, Lorentz tting of ex situ Raman spectra, XPS data and PXRD pattern of MnO x aer activation. See