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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:mrow><mml:mi>mmo</mml:mi> <mml:msub><mml:mi>l</mml:mi> <mml:msub><mml:mi>H</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:msub> <mml:msup><mml:msub><mml:mi>g</mml:mi> <mml:mi>cat</mml:mi></mml:msub> <mml:mrow><mml:mo>-</mml:mo> <mml:mn>1</mml:mn></mml:mrow> </mml:msup> <mml:msup><mml:mi>h</mml:mi> <mml:mrow><mml:mo>-</mml:mo> <mml:mn>1</mml:mn></mml:mrow> </mml:msup> </mml:mrow> <mml:annotation>${\mathrm{mmo}}{{{\mathrm{l}}}_{{{{\mathrm{H}}}_2}}}{{{\mathrm{g}}}_{{\mathrm{cat}}}}^{ - 1}{{{\mathrm{h}}}^{ - 1}}$</mml:annotation></mml:semantics> </mml:math> 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.