Comparative Study\non the Effect of Terthienyl-diphenylstyrene\nType Organic Photocatalysts for Efficient Hydrogen Evolution

Donor–acceptor (D-A) type linear conjugated polymer\nis considered\nas a promising photocatalyst due to its facile adjustment of energy\nbands and spectral range. Herein, we designed a series of D-A linear\nconjugated polymers based on terthienyl-diphenylstyrene. The comparative\neffect was investigated via ultraviolet–visible (UV–vis),\nX-ray powder diffraction (XRD), transient photocurrent response (TPR),\ncyclic voltammetry (CV), etc. The results demonstrated that incorporating\nstyryl building blocks into the acceptor moiety can efficaciously\nenhance the photocatalysis hydrogen production (PHP) activities, surpassing\nthe effect of incorporating cyano substituents into the acceptor moiety.\nAmong them, <b>BTT-PPAN</b> (<b>BTT</b> is 2,2′:5′,2″-terthiophene, <b>PPAN</b> is (2<i>Z</i>,2′<i>Z</i>)-3,3′-(1,4-phenylene)bis(2-phenylacrylonitrile))\nexhibited an outstanding PHP rate (35.54 mmol g<sup>–1</sup> h<sup>–1</sup>). The terpolymers (<b>PPAN</b><sub><b><i>x</i></b></sub><b>PFN</b><sub><b><i>y</i></b></sub>; <b>PPAN</b> is (2<i>Z</i>,2′<i>Z</i>)-3,3′-(1,4-phenylene)bis(2-phenylacrylonitrile), <b>PFN</b> is 2,3-diphenylfumaronitrile) were subsequently constructed\nby changing the feed ratio of 2,3-<i>bis</i>(4-bromophenyl)fumaronitrile\n(<b>M3</b>) and (2<i>Z</i>,2′<i>Z</i>)-2,2′-(1,4-phenylene)<i>bis</i>(3-(4-bromophenyl)acrylonitrile)\n(<b>M4</b>) and polymerization with <b>BTT</b>. The investigation\nof terpolymers also demonstrates that the conjugation length plays\na more critical role in the performance of PHP than the cyano substituent\neffect. The comparative impact result obtained in this investigation\nwill provide an invaluable theoretical guideline for the future rational\ndesign of high PHP performance materials.