Hydrazine as a hydrogen carrier in the photocatalytic generation of H₂ using CdS quantum dots

The compelling need for safe storage and transportation of H₂ has made liquid-phase materials safer H₂-carriers with a high gravimetric and volumetric hydrogen density. Unlike thermal or electrocatalytic decomposition on precious metal catalysts, a photocatalytic route to decomposing these liquid-phase materials can offer triggered onboard production of H₂ and help mitigate the safety issues concerned with H₂ storage. We have investigated visible-light induced H₂ evolution from aqueous hydrazine using CdS quantum dots (QDs) as metal-free photocatalysts. Hydrazine acts as a H₂ carrier as well as a donor, giving rise to a visible-light induced H₂ evolution activity as high as 33 mmol h^-1 g^-1 at pH 8. This has been achieved by the use of CdS QDs capped with S^2- ligands. The use of larger ligands such as mercaptopropionic acid hinders the adsorption of hydrazine onto CdS QDs and significantly decreases the activity. The effect of pH on the hydrogen yield in aqueous hydrazine has also been examined.