Decomposition of water over picene derivatives photocatalyst under visible light irradiation

5,8-dicyanopicene (CN-picene), a picene derivative that absorbs visible-light, was synthesized and its photo -catalytic activity for hydrogen production via water decomposition under visible-light irradiation was evaluated. A CN-picene thin-film deposited on a quartz substrate (CNp/Q) was produced by thermal evaporation under vacuum. Hydrogen formation was observed by subjecting CNp/Q to visible-light irradiation in the presence of water. It was confirmed by mass spectrometry using D2O that the generated hydrogen was derived from water. Water decomposition over CNp/Q photocatalysts with different film thicknesses was also investigated; hydrogen -formation activity increased with film thickness. Furthermore, scanning electron microscopy measurements showed that CN-picene was unevenly deposited on the quartz substrate owing to its aggregation. The surface roughness of the CN-picene film increased with its thickness, which consequently increased its surface area; hence, CNp/Q catalysts with thicker films had higher water-decomposition activities than their thinner counterparts.

Automated summary

5,8-dicyanopicene, a visible-light-absorbing picene derivative, was synthesized and its photocatalytic activity for hydrogen production via water decomposition was evaluated. A CN-picene thin-film deposited on a quartz substrate showed increased hydrogen formation activity with film thickness. The uneven deposition of CN-picene on the substrate resulted in increased surface roughness and higher water-decomposition activities for catalysts with thicker films.