Band structure engineering of a polyimide photocatalyst towards enhanced water splitting

Polyimide (PI), a typical donor-acceptor polymeric semiconductor, exhibits promising photocatalytic applications owing to its distinct advantages of facile synthesis, easy functionalization and molecularly tunable optoelectronic properties. However, PI in its pristine form has moderate photocatalytic activity due to non-optimal band structure and fast recombination of photo-excited charge carriers. Herein, we report the band structure engineering of PI for enhanced photocatalytic water splitting by simply tuning the feed ratio of the amine and anhydride monomer. Anhydride-rich PI possesses lower valence band position and stronger photooxidation capability, resulting in a preferential activity for water oxidation over water reduction in comparison with amine-rich PI. The structure-activity relationships revealed in this work shed light on the rational design of polymeric photocatalysts with suitable redox energetics for specific photoreactions. Band structure engineering of polymide for enhanced photocatalytic water splitting has been demonstrated by tuning the donor/acceptor ratios in the polymer skeleton.