Donor‐Acceptor Conjugated Acetylenic Polymers for High‐Performance Bifunctional Photoelectrodes

Abstract

AbstractDue to the drastic required thermodynamical requirements, a photoelectrode material that can function as both a photocathode and a photoanode remains elusive. In this work, we demonstrate for the first time that, under simulated solar light and without co‐catalysts, donor‐acceptor conjugated acetylenic polymers (CAPs) exhibit both impressive oxygen evolution (OER) and hydrogen evolution (HER) photocurrents in alkaline and neutral medium, respectively. In particular, poly(2,4,6‐tris(4‐ethynylphenyl)‐1,3,5‐triazine) (pTET) provides a benchmark OER photocurrent density of ~200 μA cm−2 at 1.23 V vs. reversible hydrogen electrode (RHE) at pH 13 and a remarkable HER photocurrent density of ~190 μA cm−2 at 0.3 V vs. RHE at pH 6.8. By combining theoretical investigations and electrochemical‐operando Resonance Raman spectroscopy, we show that the OER proceeds with two different mechanisms, with the electron‐depleted triple bonds acting as single‐site OER in combination with the C4‐C5 atoms of the phenyl rings as dual sites. The HER, instead, occurs via an electron transfer from the tri‐acetylenic linkages to the triazine rings, which act as the HER active sites. This work represents a novel application of organic‐based materials and contributes to the development of high‐performance photoelectrochemical catalysts for the solar fuels’ generation.