Conjugated diacetylene polymers with intrachain D-A block heterostructure for efficient photocatalytic hydrogen production

Abstract

Solar-driven photocatalytic hydrogen production has been considered as a promising candidate technology for supplying green and sustainable energy source alternative to fossils. But its low solar-to-hydrogen conversion efficiency level hampers its practical application, and lack of effective structure for promoting charge separation is one of the accounts. Herein, intrachain heterojunction structure comprised of donor-acceptor (D-A) blocks has been proved to be one of effective structures for addressing such an issue. Utilizing the facile oxidative coupling polymerization reactions of diacetylene monomers and oligomers, a block heterojunction polymeric photocatalyst named PDTPDPA-BP bearing D-A blocked heterostructure was synthesized by first separative oligomerizations of diacetylene-functionalized dibenzothiophene sulfone (DTP) and triphenylamine (TPA) monomers and then mixed together and undergoing further polymerization. In photocatalytic hydrogen production, PDTPDPA-BP displayed a hydrogen evolution rate of 2164 μmol g−1 h−1, which is much larger than those of PDTP (1270 μmol g−1 h−1) and PTPA (57 μmol g−1 h−1) synthesized by homopolymerization of DTP and TPA monomers, respectively, and their 1:1 molar ratio physical blend (363 μmol g−1 h−1). By means of Fluorescence spectroscopy and photo-responsive measurements, it was found PDTPDPA-BP has narrower bandgap and more efficient charge separation than the other polymers. Therefore, the work highlights intrachain heterojunction structure promotes exciton dissociation into free charge carries, and thus deserves the consideration in the design of high performance organic photocatalysts.