Side-chain-extended conjugation: a strategy for improving the photocatalytic hydrogen production performance of a linear conjugated polymer

Abstract

A side-chain-extended conjugation strategy is demonstrated here to improve the photocatalytic performance of a linear conjugated polymer for hydrogen production from water. For this, polymers P0, P1, and P2 were designed and synthesized based on benzodithiophene and dibenzothiophene S,S-dioxide. Compared with P0, P1 and P2 have two additional thiophene units conjugated in the polymer skeleton along the main-chain and side-chain directions, respectively. Studies found that side chain-conjugated functionalization in P2 enhances thermal stability, redshifts light-absorption bands, narrows the polymer bandgap, prolongs the exciton lifetime, enlarges the photocatalytic over-potential, increases charge mobility, reduces charge transport resistance, and thus improves the hydrogen evolution rate (HER) by a factor of 160 fold. Although performance improvement is still observed in P1, the factor is only 3.6 fold. Thus, P2 exhibits the most promising performance among the three polymers with a HER of 20 314 μmol g⁻¹ h⁻¹ in the presence of 3 wt% Pt cocatalyst and a record apparent quantum yield of 7.04% at 500 nm, rendering it an excellent green light photocatalyst.