▎ 摘　　要

Polyphosphate reduced graphene oxide on Ni foam (PPO-RGO/NF) is synthesized by varying weight ratios of Na5P3O10 (PO): graphene oxide (GO) with a simple, scalable and low cost method through freeze-drying of the PO-GO/NF followed by thermal treatment of the prepared electrodes. The resulting samples are characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), Brunauer-Emmett-Teller (BET), and raman spectroscopy methods. The results show that the weight ratio of PO:GO, considerably affect the electrochemical properties of PPO-RGO/NF. Especially, the as-prepared PPO-RGO/NF with PO:GO weight ratio of 2:1 delivers a high specific capacitance of 118 F g(-1) at a current density of 5 A g(-1), and also the specific capacitance reaches 108 F g(-1) with 92% capacitance retention after 3000 cycles. The good capacitive performance and cycling stability of the PPO-RGO/NF can be attributed to the collaborative effect of the electrical double layer capacitor of RGO and the pseudocapacitance characteristics from the faradaic reactions of the PPO groups. The as-prepared PPO-RGO/NF as the binder free electrode can be used to assemble a symmetric supercapacitor. Accordingly, PPO-RGO/NF based symmetrical supercapacitor with the mentioned weight ratio of PO:GO achieves some remarkable performances; good specific capacitance (30.9 F g(-1) at 1 A g(-1)), energy density (2.47 Wh kg(-1) at 523.48 W kg(-1)), and power density (2618 W kg(-1) at 0.8 Wh kg(-1)). (C) 2018 Elsevier Ltd. All rights reserved.