Construction of rGO/BP/COF high-low heterojunction for efficient photocatalytic hydrogen evolution

The covalent organic frameworks (COFs) have emerged as potential photocatalysts for solar-driven hydrogen evolution, but the disadvantage that photogenerated electrons and holes are prone to recombination limits their applications. Here, a rGO/BP/TpPa-1 high-low heterojunction with electron acceptors was prepared by integrating reduced graphene oxide (rGO) and black phosphorus (BP) into COF TpPa-1 to reduce the recombination rate of photoinduced charge carriers. The photocatalytic hydrogen evolution rate reached 18.09 mmol h−1 g−1, about 3.3 times higher than pure TpPa-1. Here, a two-step photogenerated electron transfer mechanism is proposed. Firstly, a high-low heterojunction is formed between TpPa-1 and BP through an internal electric field from BP to TpPa-1, facilitating photogenerated electrons transfer from TpPa-1 to BP, then rGO attached to the BP surface acts as an electron acceptor, further collecting photogenerated electrons for reaction. This work provides a novel strategy for synthetizing efficient COF-based photocatalysts.