Direct photocatalytic hydrogen evolution from water splitting using nanostructures of hydrate organic small molecule as photocatalysts

Abstract

Organic small molecules with a suitable energy level have usually been considered as photosensitizers rather than catalysts for photocatalytic hydrogen evolution (PHE). Herein, we achieved direct PHE using hydrate zinc tetraphenylporphyrin (ZnP, ZnTPP·H₂O) nanostructures synthesized by a liquid-phase chemical reaction as photocatalysts. The shape-dependent photocatalysis revealed that the ZnP nanosheets (ZnP-NS) exhibit higher PHE activity (∼0.16 mmol g⁻¹ h⁻¹) than the ZnP octahedron nanoparticles (ZnP-NPs) (∼0.06 mmol g⁻¹ h⁻¹). After in situ construction of the rubrene/ZnP-NS heterostructure, more efficient PHE of this pure organic nanostructure was obtained due to the occurrence of photoinduced electron transfer and Förster resonance energy transfer (FRET). The optimal PHE rate is ∼0.56 mmol g⁻¹ h⁻¹. Furthermore, with the addition of 3.0 mM methyl viologen (MV) and 3.8 wt% platinum, a PHE rate of ∼9.3 mmol g⁻¹ h⁻¹ can be achieved at pH = 7. This study offers a new route to design organic small molecules as photocatalysts.