In order to realize the reuse of agricultural waste and improve the electrochemical performance of carbon materials, N and P co-doped carbon materials were prepared by using rich and cheap waste peanut shells as carbon precursors and NH4H2PO4 as N and P sources. The effects of the mass ratio of peanut shell and NH4H2PO4 on the structure, composition, morphology and electrochemical properties of carbon materials were studied in detail. The results show that when the mass ratio is 2:3, the prepared PSC-3 has the largest surface area and higher heteroatom content, which provides a structural basis for its high electrochemical performance. Electrochemical tests show that the specific capacitance of PSC-3 at 1 A g−1 can reach 184 F g−1, and has excellent rate performance. When the mass ratio is higher than or below 2:3, the electrochemical performance of carbon materials will be reduced, demonstrating the feasibility of achieving the best electrochemical performance by adjusting the amount of NH4H2PO4. In addition, the symmetric supercapacitor (SSC) assembled by PSC-3 can obtain an energy density of 10.1 Wh kg−1, which has excellent energy storage characteristics.

One-step production of peanut shell derived N, P co-doped carbon materials for high-performance symmetric supercapacitors