An energy-dense and thermal-stable bis-azobenzene/hybrid templated assembly for solar thermal fuel

Abstract

Designing an energy-dense and thermal-stable photo-isomerizable chromophore/hybrid template is a challenge for devising a highly customizable solar-heat conversion and storage technology. This study presents the templated assembly of close-packed 2-chloro-4,6-bis(4-(phenyldiazenyl)phenoxy)-1,3,5-triazine (bis-azobenzene chromophores) covalently bound to reduced graphene oxide (RGO-bis-Azo). The steric configuration and energy of bis-Azo (trans- and cis-isomers), calculated by density functional theory, are influenced by intra- and inter-molecular steric hindrance due to high grafting density and the bundling effect. This results in a dramatic increase in enthalpy and activation energy of the isomerization. The RGO-bis-Azo hybrid combines a high energy density of 80 W h kg⁻¹, the maximum power density of 2230 W kg⁻¹ and a tunable heat release time from 2 min to 5520 h. These findings pave the way for developing a chromophore/hybrid template for solar thermal fuel by optimizing molecular interaction.