Effect of Graphene Oxide on Phase Change Materials Based on Disodium Hydrogen Phosphate Dodecahydrate for Thermal Storage.

Kaiyue Huang,Jinhong Li,Chengdong Wang,Zhiwei Yang,Xuezhu Luan,Lijie Liu

doi:10.1021/acsomega.0c01184

Abstract

A novel composite phase change material (PCM) for thermal energy storage was prepared by adding graphene oxide (GO) to melted disodium hydrogen phosphate dodecahydrate (DHPD, Na2HPO4·12H2O), which was then impregnated into expanded vermiculite (EV). Because of the addition of GO, the contact angle between melted DHPD and EV was decreased from 56 to 45°. The maximum latent heat of the composite PCM without GO was 167 J/g, which was improved to 229 J/g by adding 0.2 wt % GO. The phase change temperature of the composite PCM was around 42 °C. The results from X-ray diffraction, scanning electron microscopy, and contact angle tests revealed that the improvement in thermal energy storage was achieved because of the reduction of crystal water loss and the increased encapsulation amount of salt hydrates. Thus, the thermal stability of the composite PCM was improved by the addition of GO, which was demonstrated by thermogravimetric analysis. The results of all analyses indicate that the addition of a low weight fraction GO can promote the performance of salt hydrates existing in EV.

Highlights

Owing to the increase in population and demand for thermal comfort, building energy consumption is expected to increase steadily, half of which is energy consumed by air conditioning systems
The study of salt hydrates as phase change material (PCM) is an important topic for energy conservation, and the use of porous minerals as encapsulation matrices is an excellent option for application on building envelopes and decoration
This is the first time that a shape-stable composite PCM was prepared by adding graphene oxide (GO) to salt hydrates

Summary

INTRODUCTION

Owing to the increase in population and demand for thermal comfort, building energy consumption is expected to increase steadily, half of which is energy consumed by air conditioning systems. The applications of PCMs have been studied for air source heat pumps, floor heating, and building envelopes.[5−8] Thermal insulation layers using PCMs can reduce the effect of outdoor temperature on indoor temperature They store thermal energy at high temperatures and release it at low temperatures to heat the rooms. Graphene oxide (GO) is a suitable additive for these two demands Several functional groups, such as carboxyl and hydroxyl groups of GO, readily form hydrogen bonds with crystal water.[31,32] The skin friction coefficient of fluid increases with an increase in the GO volume fraction, thereby preventing leakage when the salt hydrate is melted.[33] GO is widely used to enhance the conductivity of photoelectric materials, biomaterials, and modified polymers.[34−37] Lu38 et al enhanced the thermal conductivity of polyurethane/wood powder composite PCMs by incorporating GO. The effects of GO on the crystal water of DHPD encapsulated in EV and on the thermal energy storage of the composite PCM were evaluated

RESULTS AND DISCUSSION

CONCLUSIONS

EXPERIMENTAL SECTION

■ ACKNOWLEDGMENTS

■ REFERENCES