Thiophene‐Based Conjugated Acetylenic Polymers with Dual Active Sites for Efficient Co‐Catalyst‐Free Photoelectrochemical Water Reduction in Alkaline Medium
Mino Borrelli, Christine Joy Querebillo, Dominik L. Pastoetter, Tao Wang, Alberto Milani, Carlo S. Casari, Hoang Khoa Ly, Fan He, Yang Hou, Christof Neumann, Andrey Turchanin, Hanjun Sun, Inez M. Weidinger, Xinliang Feng
Abstract
Abstract Although being attractive materials for photoelectrochemical hydrogen evolution reaction (PEC HER) under neutral or acidic conditions, conjugated polymers still show poor PEC HER performance in alkaline medium due to the lack of water dissociation sites. Herein, we demonstrate that tailoring the polymer skeleton from poly(diethynylthieno[3,2‐b]thiophene) ( pDET ) to poly(2,6‐diethynylbenzo[1,2‐b:4,5‐b′]dithiophene ( pBDT ) and poly(diethynyldithieno[3,2‐b:2′,3′‐d]thiophene) ( pDTT ) in conjugated acetylenic polymers (CAPs) introduces highly efficient active sites for water dissociation. As a result, pDTT and pBDT , grown on Cu substrate, demonstrate benchmark photocurrent densities of 170 μA cm −2 and 120 μA cm −2 (at 0.3 V vs. RHE; pH 13), which are 4.2 and 3 times higher than that of pDET , respectively. Moreover, by combining DFT calculations and electrochemical operando resonance Raman spectroscopy, we propose that the electron‐enriched C β of the outer thiophene rings of pDTT are the water dissociation active sites, while the −C≡C− bonds function as the active sites for hydrogen evolution.