title: Covalent functionalization of graphene by azobenzene with molecular hydrogen bonds for long-term solar thermal storage.
abstract: Reduced graphene oxide-azobenzene (RGO-AZO) hybrids were prepared via covalent functionalization for long-term solar thermal storage. Thermal barrier (ΔEa) of cis to tran reversion and thermal storage (ΔH) were improved by molecular hydrogen bonds (H-bonds) through ortho- or para-substitution of AZO. Intramolecular H-bonds thermally stabilized cis-ortho-AZO on RGO with a long-term half-life of 5400 h (ΔEa = 1.2 eV), which was much longer than that of RGO-para-AZO (116 h). RGO-para-AZO with one intermolecular H-bond showed a high density of thermal storage up to 269.8 kJ kg(-1) compared with RGO-ortho-AZO (149.6 kJ kg(-1)) with multiple intra- and intermolecular H-bonds of AZO according to relaxed stable structures. Thermal storage in experiment was the same order magnitude to theoretical data based on ΔH calculated by density functional theory and packing density. Photoactive RGO-AZO hybrid can be developed for high-performance solar thermal storage by optimizing molecular H-bonds.
authors.affiliation: School of Materials Science and Engineering, Tianjin Key Laboratory of Composite and Functional Materials, Tianjin University, Tianjin 300072, China.
authors.forename: Yiyu
authors.initials: Y
authors.lastname: Feng
authors.forename: Hongpo
authors.initials: H
authors.lastname: Liu
authors.forename: Wen
authors.initials: W
authors.lastname: Luo
authors.forename: Enzuo
authors.initials: E
authors.lastname: Liu
authors.forename: Naiqin
authors.initials: N
authors.lastname: Zhao
authors.forename: Katsumi
authors.initials: K
authors.lastname: Yoshino
authors.forename: Wei
authors.initials: W
authors.lastname: Feng