Comparative Study on the Effect of Terthienyl-diphenylstyrene Type Organic Photocatalysts for Efficient Hydrogen Evolution

Donor–acceptor (D-A) type linear conjugated polymer is considered as a promising photocatalyst due to its facile adjustment of energy bands and spectral range. Herein, we designed a series of D-A linear conjugated polymers based on terthienyl-diphenylstyrene. The comparative effect was investigated via ultraviolet–visible (UV–vis), X-ray powder diffraction (XRD), transient photocurrent response (TPR), cyclic voltammetry (CV), etc. The results demonstrated that incorporating styryl building blocks into the acceptor moiety can efficaciously enhance the photocatalysis hydrogen production (PHP) activities, surpassing the effect of incorporating cyano substituents into the acceptor moiety. Among them, BTT-PPAN (BTT is 2,2′:5′,2″-terthiophene, PPAN is (2Z,2′Z)-3,3′-(1,4-phenylene)bis(2-phenylacrylonitrile)) exhibited an outstanding PHP rate (35.54 mmol g^–1 h^–1). The terpolymers (PPAN_xPFN_y; PPAN is (2Z,2′Z)-3,3′-(1,4-phenylene)bis(2-phenylacrylonitrile), PFN is 2,3-diphenylfumaronitrile) were subsequently constructed by changing the feed ratio of 2,3-bis(4-bromophenyl)fumaronitrile (M3) and (2Z,2′Z)-2,2′-(1,4-phenylene)bis(3-(4-bromophenyl)acrylonitrile) (M4) and polymerization with BTT. The investigation of terpolymers also demonstrates that the conjugation length plays a more critical role in the performance of PHP than the cyano substituent effect. The comparative impact result obtained in this investigation will provide an invaluable theoretical guideline for the future rational design of high PHP performance materials.