Manganese oxide - carbon composites consisting in Hausmannite Mn3O4 nanoparticles and Vulcan carbon were prepared by in situ autocombustion method (ISAC). The electrochemical properties of the composites and their pseudo-capacitance have been evaluated at different pH. The composites with optimized carbon content demonstrated at pH = 14 high specific oxide capacitance (754 F/g of oxide at 1 mV/s) with just a moderate decrease at higher sweep rate (439 F/g at 500 mV/s). Relatively fast and reversible redox transformations of Mn3O4 into substoichiometric possibly hydrated oxides were tentatively proposed as the main processes responsible for observed pseudo-capacitance. High oxide capacitance suggested that the bulk of oxide particles is participating in charge storage. Systematic decrease of the reversibility and contribution of these redox processes into pseudo-capacitance was detected when pH decreases from 14 to 10. A continuous decrease in capacitance during 10000 galvanostatic cycles was observed at high pH (13 and 14); however, capacitance stabilized at lower pH after a drop during first few thousand cycles. (C) 2016 Elsevier Ltd. All rights reserved.