Self-template and self-activation synthesis of nitrogen-doped hierarchical porous carbon for supercapacitors

Abstract

Hierarchical porous texture is regarded as an ideal design for carboneous electrode materials of supercapacitors as it can present both high capacitance and good rate performance. Here, we propose a very simple and effective strategy to prepare nitrogen-doped, hierarchical porous carbons by direct pyrolysis of ethylenediamine tetraacetic acid disodium zinc salt, which plays multi-roles of carbon precursor, nitrogen source, hard template and activation agent all in one. During the pyrolysis process, ethylenediamine tetraacetic acid disodium zinc salt is firstly decomposed to a composite of nitrogen-doped carbon, nano-ZnO and Na2CO3 particles. The nano-ZnO and Na2CO3 particles are evenly embedded in the carbon matrix, acting as hard templates to create mesopores. Furthermore, the nano-ZnO also contributes to micropore creation as an activation agent at further increasing temperature. As a result, the nitrogen-doped, hierarchical porous carbons are easily obtained. The large surface area (1368 m2 g−1) and high nitrogen content (6.71 at%) enable the carbon prepared at 700 °C exhibits a high capacitance of 275 F g−1 and excellent rate capability (207 F g−1 at 100 A g−1) in 6 mol L−1 KOH aqueous electrolytes, indicating a promising candidate as a carbon electrode material for supercapacitors.