Recent advances on nitrogen doped porous carbon micro-supercapacitors: New directions for wearable electronics

In pursuit of the proper use of renewable energy, researchers have been actively looking for suitable energy storage materials. Porous carbon (PC) derived from biomass has large surface area, high electrical conductivity, low manufacturing cost and environment-friendly nature, and therefore it is considered an ideal choice, as an electrode material for energy storage devices. The N-doping can further enhance the physicochemical/electrochemical properties of PC. The rapid development in the wearable electronics has inspired the call for miniaturized energy storage devices. Due to their long cyclic lifetime, high power density and rapid charging/ discharging, micro-supercapacitors (MSCs) have drawn considerable attention. In the current decade, the main emphasis has been on improving the energy density of MSCs. Therefore, with the aim of improving the electrochemical performance of MSCs, researchers have focused their attention on electrode materials. It has been found that electrode material and electrode design is important for the performance of MSCs. The present review focuses on the current developments in the MSCs. In this review, we discuss various techniques employed for the preparation of MSCs. Subsequently, the focus has been on PC derived from biomass and their N-doping by conventional (using Nitrogen precursor with biomass) and self-doped (only biomass). Further, few Nitrogendoped PC based MSCs have been discussed and a capacitance as large as 36.5 mF cm-2 has been noted. It is therefore believed that the NPC strategy may offer several prospects in the advancement of low-cost and highperformance MSCs on a large scale for commercial applications.