Two-channel photocatalytic production of H2O2 over g-C3N4 nanosheets modified with perylene imides

Hydrogen peroxide is a promising solar fuel and widely used in many industrial processes. Here we report on a new basis for clean energy storage, generating H2O2 from H2O and O2 by organic photocatalysis. In this study, we construct an all-solid-state Z-scheme heterojunction (PIx-NCN) by assembling perylene imides (PI) on g-C3N4 nanosheets (NCN), where x is a percentage weight ratio of PI to NCN. PIx-NCN exhibits significant enhancement in photocatalytic production H2O2, and the maximum enhancement was observed for PI5.0-NCN. It was shown that PI can change H2O2 generation from single-channel to two-channel. Specifically, photoexcitation of the PI moieties transfers their conduction band electrons to the valence band of NCN, resulting in enhanced charge separation. Thus, more electrons are available to reduce O2, producing more H2O2. More importantly, the holes in the valence band of PI moiety have more positive potential (2.08 V) than those of NCN (1.63 V), which can oxidize OH− to form OH (1.99 V) and transform to H2O2 via the second channel. Therefore, for PIx-NCN, the photogenerated electrons and holes can be separated into two different phases, helping spatially isolate the oxidation and reduction reaction sites, and thus minimizing the catalytic deactivation.