Step potential electrochemical spectroscopy (SPECS) has been applied to nitrogen-doped and non-doped hydrothermal carbons that have been activated or heat-treated at a range of temperatures. The highest surface area achieved was 422 m(2).g(-1) under heat-treatment at 600 degrees C, and 2275 m(2).g(-1) using H3PO4 chemical activation at 800 degrees C. The heat-treated series reported a maximum capacitance of 84 F.g(-1) at 10 mV.s(-1), whereas the activated series had a maximum capacitance of 306 F.g(-1) at 10 mV.s(-1) . SPECS analysis revealed that pseudo-capacitance for the hydrothermal carbon doped with nitrogen was interlinked with the degree of oxygen functionality, and that decreasing the oxygen content of the surface increased the pseudo-capacitance contribution from nitrogen. Pseudo-capacitance also increased with activation from the incorporation of phosphate groups; however, the nitrogen-doped hydrothermal carbons displayed minimal double-layer capacitance (60.6 F.g(-1) at 10 mV.s(-1)) despite having reasonable surface areas (1500-1600 m(2).g(-1)). (C) 2018 The Electrochemical Society.