Graphene oxide papers with high water adsorption capacity for air dehumidification

Renlong Liu,Kan Zhang,Changgu Lee,Tao Gong

doi:10.1038/s41598-017-09777-y

Abstract

Graphene oxide (GO) has shown a high potential to adsorb and store water molecules due to the oxygen-containing functional groups on its hydrophilic surface. In this study, we characterized the water absorbing properties of graphene oxide in the form of papers. We fabricated three kinds of graphene oxide papers, two with rich oxygen functional groups and one with partial chemical reduction, to vary the oxygen/carbon ratio and found that the paper with high oxygen content has higher moisture adsorption capability. For the GO paper with reduction, the overall moisture absorbance was reduced. However, the absorbance at high humidity was significantly improved due to direct formation of multilayer water vapor in the system, which derived from the weak interaction between the adsorbent and the adsorbate. To demonstrate one application of GO papers as a desiccant, we tested grape fruits with and without GO paper. The fruits with a GO paper exhibited longer-term preservation with delayed mold gathering because of desiccation effect from the paper. Our results suggest that GO will find numerous practical applications as a desiccant and is a promising material for moisture desiccation and food preservation.

Highlights

Direct dispersion in water of graphene sheets, which have a high specific surface area[1, 2], is generally considered unattainable[3, 4], owing to their hydrophobic nature[5]
If oxygen functional groups are introduced onto graphene flakes through oxidation or other chemical reaction[6], water molecules can readily intercalate into the interlayer galleries of the functionalized graphite[7, 8], suggesting that graphene can be used as a water absorbent[9, 10]
RGO fabricated from this low temperature thermal reduction process contained far less oxygen-containing functional groups (Fig. 1c)[26]

Summary

Introduction

Direct dispersion in water of graphene sheets, which have a high specific surface area[1, 2], is generally considered unattainable[3, 4], owing to their hydrophobic nature[5]. It is known that functional groups in the GO structure open gaps between the stacked platelets that are approximately 1 nm wide[14, 17] These gaps in GO paper provide channels for transportation and storage of water molecules. These hydrophilic groups can adsorb and retain water molecules forming hydrogen bonds. We systematically examined the characteristics of moisture adsorption of GO paper with different conditions of surface functionalization. The adsorption capability of kGO was found to be higher than that of hGO and rGO due to the differences in their capillary sizes and the amount of hydrophilic groups. We observed that the mechanism of water molecule adsorption varied depending on the density of the functional groups. We tested the adsorption of several organic molecules to demonstrate the feasibility of utilizing GO as an effective physical adsorption desiccant

Methods

Results

Conclusion