Naturally hierarchical nanostructures of leaves were successfully replicated on thermally stable polyimide (PI) films to obtain biomimetic substrates for the grafting of p-type semiconductor, cuprous oxide (Cu2O). The chemical states of Cu2O and the hydrophobicity on the photocatalytic films were tunable by altering the process time of ion-exchange or chemical reduction. The obtained photocatalytic films showed activity to photocatalytically convert carbon dioxide (CO2) into carbon monoxide (CO) under visible light illumination. The yield of CO was initially improved with the increasing hydrophobicity on the film but then leveled off. The photocatalytic activity could be further improved by tailoring the amount or composition of copper oxides. An optimum ratio of Cu2O and moderate basicity on the surface, as well as more metallic Cu from the bulk, will achieve more efficient interfacial charge transfer, resulting in a higher CO production rate.
Keywords: XANES; biomimetic; copper; cuprous oxide; hydrophobicity; polyimide.