To further improve the capacitive performances of reduced graphene oxide-based materials is still crucial although N-doped reduced graphene oxide hydrogels (NrGOHs) exhibit fairly good performance. Here the purified NrGOHs (NrGOHs-SA) are obtained by treating the NrGOHs which are hydrothermally synthesized in the presence of o-phenylenediamine (oPDA) with concentrated sulfuric acid. The effect of preparation conditions on the hydrogels' electrochemical behavior has been systematically investigated. The results reveal that the capacitive performances of NrGOHs-SA are remarkably enhanced compared with the samples of NrGOHs. The optimal NrGOH-SA shows specific capacitance about 519.8 F g(-1) at low scan rate, and excellent rate capability. The cells assembled by the optimal hydrogels exhibit the maximum energy density of 11.1 Wh kg(-1) and power density of 14.1 kW kg(-1), and can retain 93.3% of its initial capacitance after 15,000 cycles. This method can be developed to prepare high-performance NrGOHs materials for energy storage applications.