Enhanced photocatalytic H2 evolution based on a polymer/TiO2 film heterojunction

Polymer heterojunctions have emerged as promising photocatalysts for the photocatalytic hydrogen evolution . However, they are usually used in the form of suspended powder due to the low solubility and lack of anchoring groups to hybridize with inorganic semiconductor oxides . Yet polymer film heterojunctions with convenient separation and recycling potential are more suitable for large-scale water splitting. Herein, a new solution-processable polymer PDBCOOH with biphenyl as the electron donor and diketopyrrolopyrrole (DPP) containing carboxyl group as the electron acceptor has been designed and synthesized. Surface anchoring of PDBCOOH to TiO 2 films through covalent bonding formed polymer-TiO 2 film heterojunctions that achieved a recorded photocatalytic H 2 production rate of 11.9 mmol/m 2 /h without Pt co-catalyst and was 88.8 times higher than that of pristine TiO 2 film. Transient absorption spectroscopy confirms ultrafast polymer excited state electron injection into TiO 2 , long-lived charge separated state, and unity yield of polymer hole regeneration. Photoelectrochemical experiments combined with density functional theory calculation further demonstrate that polymer PDBCOOH /TiO 2 film heterojunctions not only accelerate the charge transfer but also significantly improve the hydrogen evolution rate and stability of the photocatalysts. This work offers a new strategy for obtaining stable and efficient photocatalysts by using the covalent anchoring strategy of polymer/TiO 2 film heterojunction.