Linear multiple-thiophene-containing conjugated polymer photocatalysts with narrow band gaps for achieving ultrahigh photocatalytic hydrogen evolution activity under visible light

Abstract

Photocatalytic hydrogen production based on dibenzothiophene-S,S-dioxide (BTDO)-containing polymer photocatalysts has attracted much attention in recent years, due to the high hydrophilicity and strong electron withdrawing capability of BTDO. However, most reported BTDO-containing photocatalysts still suffer from low photocatalytic activity under visible light irradiation. Herein, two multiple-thiophene-based electron donors (D) with narrow band gaps are coupled with a BTDO electron acceptor (A) to construct two D–A type polymer photocatalysts with a broad light absorption range. A comparative study on the two resulting polymer photocatalysts revealed that the small structural change of the donor unit could lead to a large difference in the photocatalytic activity of the polymer photocatalysts. Compared with TP-BTDO-1 with the dithieno[3,2-b:2′,3′-d]thiophene donor, TP-BTDO-2 containing the 2,2′:5′,2′′-terthiophene donor shows a stronger absorption for visible light, more efficient separation of charge carriers and an enhanced contact interface between the polymer photocatalyst and the photocatalytic reaction solution. Thus, TP-BTDO-2 shows a much higher photocatalytic activity with an ultrahigh photocatalytic hydrogen evolution rate (HER) of 108.59 mmol h⁻¹ g⁻¹ under visible light (λ > 420 nm) without adding a Pt co-catalyst. After loading 1 wt% Pt co-catalyst, the HER of TP-BTDO-2 could be further improved to 161.28 mmol h⁻¹ g⁻¹ under full spectrum light irradiation (λ > 300 nm).