Bandgap engineering of novel peryleno[1,12-bcd]thiophene sulfone-based conjugated co-polymers for significantly enhanced hydrogen evolution without co-catalyst

Abstract

Low-cost conjugated polymers as efficient photocatalytic semiconductors for hydrogen evolution have attracted worldwide attention in recent years. However, the narrow visible-light absorption spectrum, fast electron–hole recombination and expensive co-catalysts have limited their large-scale practical application in water splitting. In this work, we first developed the new peryleno[1,12-bcd]thiophene sulfone unit with extended π-conjugation, then prepared a series of sulfone-based hybrid conjugated co-polymers (PS-1–PS-8) by statistically adjusting the molar ratio of the monomer. The experimental results and DFT calculations indicated that with the gradual increase in the peryleno[1,12-bcd]thiophene sulfone contents in the polymer backbone, the optical bandgaps of co-polymers could be fine-tuned from 2.72 eV to 1.58 eV, and showed a red-shift in the visible-light region for improving the light-capturing capability. Besides, the internal charge separation capability along the co-polymers (PS-1–PS-8) was promoted. However, the driving force for proton reduction and the dispersibility of these co-polymers in aqueous solution were gradually decreased. When the molar ratio of dibenzo[b,d]thiophene sulfone to peryleno[1,12-bcd]thiophene sulfone was 19 : 1, the polymer PS-5 achieved the highest hydrogen evolution rate (HER), so far, of 7.5 mmol h⁻¹ g⁻¹ without co-catalyst under visible light, with an apparent quantum yield (AQY) of 15.3% at 420 nm. The HER performance was almost 3 times higher than that of the typical dibenzo[b,d]thiophene sulfone-based conjugated polymer P7. This work provides a strategy for maximizing the HERs of organic semiconductors by balancing the bandgap, charge recombination, driving force and wettability.