Tuning the Nanoporous Structure of Carbons Derived from the Composite of Cross-Linked Polymers for Charge Storage Applications.

Farshad Barzegar,Abdulhakeem Bello,Xiaohua Xia,Vladimir Pavlenko,Muhammad Zahid,Kenneth I. Ozoemena,Ncholu Manyala,Qamar Abbas

doi:10.1021/acsaem.0c02908

Abstract

Controlling the porosity of carbon-based electrodes is key toward performance improvement of charge storage devices, e.g., supercapacitors, which deliver high power via fast charge/discharge of ions at the electrical double layer (EDL). Here, eco-friendly preparation of carbons with adaptable nanopores from polymers obtained via microwave-assisted cross-linking of poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) is reported. The polymeric hydrogels possess porous and foam-like structures, giving excellent control of porosity at the precursor level, which are then subjected to activation at high temperatures of 700–900 °C to prepare carbons with a surface area of 1846 m2 g–1 and uniform distribution of micro-, meso-, and macropores. Then, graphene as an additive to hydrogel precursor improves the surface characteristics and elaborates porous texture, giving composite materials with a surface area of 3107 m2 g–1. These carbons show an interconnected porous structure and bimodal pore size distribution suitable for facile ionic transport. When implemented in symmetric supercapacitor configuration with aqueous 5 mol L–1 NaNO3 electrolyte, a capacitance of 163 F g–1 (per average mass of one electrode) and stable evolution of capacitance, coulombic, and energy efficiency during 10 000 galvanostatic charge/discharge up to 1.6 V at 1.0 A g–1 have been achieved.

Highlights

To meet the increasing energy demand of the modern world and to fill the niches requiring fast energy delivery and its simultaneous quick recovery,[1−5] new materials and methods are desirable
Carbon materials make up to 90 wt % of the electrode composition used in capacitive charge storage technologies such as supercapacitors, which are attractive devices for capturing energy from regenerative braking in tramways or in a start−stop system for automobiles.[6−8] Commercial carbons are mainly derived from biomass sources with predefined natural structure,[9−11] restricting the control over efficient storing and releasing of charges and their viability in an ever-growing energy sector
Leaving aside the discussion related with a particular probe for estimating surface and pore sizes, one would still argue over the importance of pore and ion size compatibility, which is further evidenced when ionic liquids are used as electrolytes for charge storage in nanoporous carbons.[16,17]

Summary

■ INTRODUCTION

To meet the increasing energy demand of the modern world and to fill the niches requiring fast energy delivery and its simultaneous quick recovery,[1−5] new materials and methods are desirable. Cross-linked porous polymers offer a great opportunity to control porous structure, surface area, and adsorption properties.[23,24] As a result of the controlled porosity at different length scales, such materials possess interconnected pore structure that facilitates the diffusion of ions and molecules.[25] Previously, polymer-based precursors have been carbonized and activated to prepare carbons and some of them have been efficiently used for charge storage application.[26−30] no systematic porous texture was studied owing to the absence of predefined precursor’s structural footprints. We show the use of cross-linked polymer-based precursor to obtain carbons with a wide range of pore diameter fitting the size of the maximum number of ions and efficiently charging the EDL (Figure 1), and preparing precursor composites with graphene to further improve the charge storage capability of these carbons.[31−33]. The corresponding specific energy, areal energy, specific power, and areal power for the symmetric cell are calculated according to eqs 4 and 7

■ RESULTS AND DISCUSSION

■ CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES