Hydroxyl group functionalized graphene oxide nanosheets as additive for improved erythritol latent heat storage performance: A comprehensive evaluation on the benefits and challenges

Abstract

Graphene oxide (GO) nanosheets were employed as the additive to make composites of erythritol, a promising medium-temperature PCM candidate. GO nanosheets modified with hydroxyl groups were applied to improve the dispersion stability of the composites. A systematic characterization on the latent heat storage performance was performed for both pure and composite erythritol, in order to identify the benefits and challenges of the composites. It was found that the thermal conductivity is increased by nearly twice and the degree of supercooling was lowered from ~64 °C to ~48 °C at the loading of 1.0 wt% GO nanosheets (the maximum loading tested). The addition of GO nanosheets also leads to an increase of the retrievable latent heat during crystallization, from ~187 kJ/kg to ~225 kJ/kg at the same loading, by increasing the crystallinity. However, the introduction of GO nanosheets can also lead to a rise in the dynamic viscosity of erythritol. As a result, the crystallization rate is slowed down and accordingly, the duration of crystallization becomes 62% longer when the loading reaches 1.0 wt%. In addition, favorable dispersion stability of the erythritol composites is observed, and their melting point (~117 °C) remains almost unchanged during 50 melting-crystallization cycles. Functionalized GO nanosheets have been shown to be an efficient additive for improving the performance of erythritol, but a trade-off analysis on the loading would be required to achieve the best overall performance.