Controlled Synthesis of Nitro-Terminated Oligothiophene/Crystallinity-Improved g-C 3 N 4 Heterojunctions for Enhanced Visible-Light Catalytic H 2 Production.

It is highly desired to explore closely contacted polymer semiconductor/g-C 3 N 4 heterojunction photocatalysts with promoted photogenerated-carrier separation and extended visible-light response for efficient visible-light-driven H 2 production. Here, we first synthesized the nitro-terminated oligothiophene (OTh) by the controlled copolymerization of thiophene and 2-nitrothiophene monomers, then constructed the nitro-terminated oligothiophene/crystallinity-improved g-C 3 N 4 (OTh/g-C 3 N 4 ) heterojunctions by a grinding-induced combination strategy. The ratio-optimized 20OTh 5 /g-C 3 N 4 shows highly efficient H 2 production activity up to 3.63 mmol h -1 g -1 under visible-light irradiation, with ∼25.9-time enhancement compared to that of g-C 3 N 4 . As verified by time-resolved photoluminescence spectra, surface photovoltage spectra, and the fluorescence spectra related to •OH amounts, the improved photocatalytic activity is due to the promoted photogenerated-carrier transfer and separation in the heterojunctions and the expanded visible-light response. It is also confirmed that the controlled OTh chain length, improved g-C 3 N 4 crystallinity, and tight interface contact dependent on the hydrogen bonds and N···S interactions between OTh and g-C 3 N 4 are reasonable for enhanced photogenerated-carrier separation with the electron transfer from OTh to g-C 3 N 4 . This work illustrates a feasible strategy to construct efficient polymer semiconductor/g-C 3 N 4 heterojunction photocatalysts for solar-light-driven H 2 production.