Organosilica-based ionogel derived nitrogen-doped microporous carbons for high performance supercapacitor electrodes

Abstract

The article presents the synthesis and properties of new organosilica-based ionogels for carbon precursors. A new preparation process using functional ionic liquid 1-propionic acid-2-methyl imidazole bromide as the linker and an organically modified silica framework as the host yields stable, yellowish and transparent organosilica ionogels. The ionogel is formed by (1) the sol–gel process of an organosilane [3-(2-aminoethylamino)propyl]trimethoxysilane and (2) the covalent interaction of a carboxyl-functional group of the ionic liquid with the amino-containing organosilica. Furthermore, controllable synthesis of nitrogen-doped microporous carbons from the direct pyrolysis of organosilica-based ionogels is reported. The ionic liquid serves as carbon and nitrogen sources, while the organically modified silica framework acts as an inherent template to induce porosity. As a result, high surface areas of up to 1107 m² g⁻¹ and high nitrogen contents of up to 3.9 wt% are achieved. The electrode prepared from C-1000 delivers a remarkable capacity of 254 F g⁻¹ at a current density of 1 A g⁻¹, which can be attributed to the synergistic coupling effect of N-doping, hierarchical porosity and intrinsic defects.