Porosity and Surface Modifications on Carbon Materials for Capacitance Improvement

Abstract

Supercapacitors (SC) are energy storage devices with higher power but lower energy density than Li batteries. SC store energy based on two mechanisms: double layer capacitance (non-Faradaic) and pseudocapacitance (faradaic). Porous carbon materials have been extensively used as electrodes in SC, where their great surface area and pore size distribution have been the main properties for capacitance improvement. Nevertheless, these properties have shown limitations since they cannot be highly increased without losing electric conductivity, which is detrimental for the power requirements of SC. An alternative approach to increase capacitance has been the surface modification of carbon materials by introducing faradaic contributions. In this mini review, the effect of surface area, porosity, surface modification by doping or functionalization, and introduction of electroactive oxides are discussed to show how these factors influences the intrinsic capacitance values of different carbon materials; and some examples from our work are provided. The manipulation of such properties, on carbon materials (porosity and /or surface chemistry) not only are useful for devices such as SC, but also are very useful for a wide variety of Bio-applications (Bio-sensors, labelling and drug delivery, impregnation with microorganisms for its use as biochar, or for bio-fuel cells, etc.)