Controlling Heat Release from a Close‐Packed Bisazobenzene–Reduced‐Graphene‐Oxide Assembly Film for High‐Energy Solid‐State Photothermal Fuels

A closed‐cycle system for light‐harvesting, storage, and heat release is important for utilizing and managing renewable energy. However, combining a high‐energy, stable photochromic material with a controllable trigger for solid‐state heat release remains a great challenge for developing photothermal fuels (PTFs). This paper presents a uniform PTF film fabricated by the assembly of close‐packed bisazobenzene (bisAzo) grafted onto reduced graphene oxide (rGO). The assembled rGO–bisAzo template exhibited a high energy density of 131 Wh kg−1 and a long half‐life of 37 days owing to inter‐ or intramolecular H‐bonding and steric hindrance. The rGO–bisAzo PTF film released and accumulated heat to realize a maximum temperature difference (DT) of 15 °C and a DT of over 10 °C for 30 min when the temperature difference of the environment was greater than100 °C. Controlling heat release in the solid‐state assembly paves the way to develop highly efficient and high‐energy PTFs for a multitude of applications.