Conjugated Polyelectrolyte Photocatalysts: The Use of Zwitterionic Side Groups for High Performance

Conjugated polyelectrolytes have emerged as a class of organic photocatalysts for light-driven hydrogen production from water due to their photoactive conjugated backbones and hydrophilic ionic side chains. However, compared to well-documented anionic and cationic side chains, zwitterionic side chains have been rarely reported. Herein, based on the thiophene (T)-dibenzo[b,d]thiophene sulfone (DBTSO) donor–acceptor backbone, a zwitterionic side chain-modified polymer PTDBTSO-ZS as well as an alkylated polymer PTDBTSO-C6, a cationic polymer PTDBTSO-QA, and an anionic polymer PTDBTSO-SS has been synthesized and studied. It was found that zwitterionic side chain modification can endow the polymer with good hydrophilicity, a large proportion of excited energy used for charge separation, long-lived excitons, reinforced interchain interactions, and the smallest interfacial charge transfer resistance. Consequently, PTDBTSO-ZS behaves the best in the family with a hydrogen evolution rate of 55.2 mmol g –1 h –1 under full-arc Xe light irradiation, which is 1.4-, 1.7-, and 10.0-fold as compared to those of PTDBTSO-QA, PTDBTSO-SS, and PTDBTSO-C6, respectively.