Gold nanoparticle-based supramolecular approach for dye-sensitized H 2 -evolving photocathodes.

Solar conversion of water into the storable energy carrier H ₂ can be achieved through photoelectrochemical water splitting using light adsorbing anodes and cathodes bearing O ₂ and H ₂ evolving catalysts, respectively. Herein a novel photocathode nanohybrid system is reported. This photocathode consists of a dye-sensitized p-type nickel oxide (NiO) with a perylene-based chromophore ( PCA ) and a tetra-adamantane modified cobaloxime reduction catalyst ( Co ) that photo-reduces aqueous protons to H ₂ . An original supramolecular approach was employed, using β-cyclodextrin functionalized gold nanoparticles ( β-CD-AuNPs ) to link the alkane chain of the PCA dye to the adamantane moieties of the cobaloxime catalyst ( Co ). This new architecture was investigated by photoelectrochemical measurements and via femtosecond-transient absorption spectroscopy. The results show that irradiation of the complete NiO| PCA|β-CD-AuNPs|Co electrode leads to ultrafast hole injection into NiO (π = 3 ps) from the excited dye, followed by rapid reduction of the catalyst, and finally H ₂ evolution.