Magnesium Hydroxide Templated Hierarchical Porous Carbon Nanosheets as Electrodes for High-Energy-Density Supercapacitors

Hierarchical porous carbon nanosheet (HPCN) materials of different thicknesses were fabricated on Mg(OH)2 substrates utilizing a one-step chemical vapor deposition (CVD) approach. The templated carbon nanosheets are closely packed hierarchical nanostructures possessing high surface areas varying from 1323 to 1978 m2·g–1. Symmetrical electrochemical double-layer capacitors (EDLCs) were constructed using the HPCN and demonstrated a high specific capacitance of 205 F·g–1 at 5 mV/s using 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl)imide (EMIM-TFSI) as an electrolyte. The energy density was 86 Wh·kg–1, and a power density of up to 16.57 kW·kg–1 was observed. After 5000 charge–discharge cycles at 10 A·g–1, the supercapacitor retained 90% of its initial capacity. This illustrates the great stability of the templated mesoporous carbon sheets for supercapacitors.