All-cellulose-based freestanding porous carbon nanocomposites and their versatile applications

Xueying Kong,Chao Xu,Maria Strømme,Shengyang Zhou

doi:10.1016/j.compositesb.2021.109602

Abstract

Porous carbons are key functional materials in a range of industrial processes such as gas adsorption and separation, water treatment, and energy conversion and storage. It is, however, important from a sustainability perspective for porous carbons to be synthesized from naturally abundant biopolymers. Nanoengineering of porous carbons using facile binder-free techniques presents significant challenges, but is deemed beneficial for broadening their field of use and improving their application performance. This paper discusses the processing of cellulose-based porous carbons interwoven with cellulose nanofibers to fabricate freestanding nanopapers and aerogels, aiming at developing processable, fully sustainable, and all-cellulose-based carbon nanocomposites. The aerogels, which have cellular networks, low density and high mechanical strength, were investigated as sorbents for CO 2 capture and removal of various organics. The presence of rich ultramicropores allows the aerogels to adsorb relatively high amounts of CO 2 , with high selectivity of CO 2 -over-N 2 (up to 111). More importantly, the sorbents have high CO 2 working capacities and excellent recyclability under temperature swing adsorption conditions. In addition, the aerogels can adsorb various organic solvents remarkably well, corresponding to 100–217 times their own weight. The nanopapers are active photothermal materials that can be applied as solar absorbers for interfacial solar vapor generation, providing a high evaporation rate (1.74 kg m −2 h −1 under one sun illumination). The nanopapers were also employed as electrodes in flexible, foldable supercapacitors with high areal capacitances. This study may provide a basis for further development of and new application areas for all-cellulose-based nanocomposites. • All-cellulose-based freestanding porous carbon aerogels and nanopapers were designed. • The elastic aerogels were efficient sorbents for CO 2 separation and removal of VOCs. • The freestanding nanopapers was applied for interfacial solar vapor generation. • The freestanding nanopaper electrodes were assembled into flexible supercapacitors.

Highlights

Porous carbon materials have been the object of research interest because of their practical applications in many important industrial processes [1,2]
The raw Cladophora cellulose (CC) powder was composed of micro-flower-shaped particles of a few microns in diameter with a wrinkled surface, while the microflowers were composed of intertwined nanofibers with a thickness of ≈30 nm (Fig. S2a) [55]
The nanofibrous structure led to the formation of mesopores with a diameter of 30 nm and a relatively high surface area of 85 m2 g− 1 for CC

Summary

Introduction

Porous carbon materials have been the object of research interest because of their practical applications in many important industrial processes [1,2] They have been used as sorbents for gas separation [3], filters for water and air cleaning [4,5,6], solar absorbers for photothermal conversion [7,8,9], and electrodes for electrochemical energy storage and conversion [10,11]. Most of the hydrogen and oxygen elements in the bio-precursors are released during the carbonization process via pyrolysis in an inert atmosphere (e.g., N2, Ar) [19] or with hydrothermal treatment under elevated pressures [20], yielding carbon-rich bio-chars with a non-porous structure When the latter step takes place at a high temperature in the presence of an acti vation agent (e.g., inorganic base, acid or salts), abundant pores are generated in the carbon materials. There is an increasing research interest in using advanced technology to develop sustainable porous carbons via facile synthesis methods and to overcome this poor processability

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