Solar-Driven Reversible Hydrogen Storage of Sodium Cyclohexanolate/Phenoxide Pair

Reversible hydrogen storage is a key challenge for the implementation of hydrogen energy, with dehydrogenation being particularly difficult because of its endothermic nature, slow kinetics, poor selectivity, etc. Solar energy-driven hydrogen uptake/release represents an interdisciplinary approach that provides an effective solution to those problems. Herein, we report the solar-driven reversible hydrogen uptake of 4.9 wt.% over sodium cyclohexanolate/phenoxide pair, achieving over 99.9% conversion and selectivity in both hydrogenation and dehydrogenation via photocatalysis without external heating. Notably, the initial dehydrogenation rate reaches 23.4 $\mathrm{mmo}{l}_{H_2}{g_{\mathrm{cat}}}^{-1}{h}^{-1}$ that is ca. 2 orders of magnitude higher than thermocatalysis. The superior photocatalytic performance stems from the synergy between high- and low-frequency light, i.e., low-frequency light mainly provides heat, high-frequency light drives the desorption of product from the catalyst surface. This approach offers a path toward a sustainable solar-driven hydrogen energy system.