Problem: Large-scale adoption of solar thermal fuels requires enhanced energy storage capacity and thermal stability. Previous solar thermal fuels degraded after only a few cycles of energy conversion and release and/or were composed of expensive non-abundant elements. Technology: The invention suggests a new approach to the design of high-energy density solar thermal fuels based on combining well-studied photoswitch molecules with carbon nanotubes to increase energy storage capacity and thermal stability of the photoswitch molecules. The novel solar thermal fuel is composed of azobenzene-functionalized carbon nanotubes and can have both volumetric and gravimetric energy densities comparable to that of Li-ion batteries.
1) No emissions 2) Easily transportable in liquid or powder form 3) Easy to recharge 4) Can cycle through energy conversion and release numerous times without degradation 5) CNT substrate imposes close-packed highly ordered array of adsorbed photomolecules which leads to increased volumetric energy density 6) Enables systematic manipulation of the inter- and intra-molecular interactions creating a highly effective set of tuning parameters for maximizing both energy storage capacity and storage lifetime of the solar thermal fuel