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Thiophene‐Bridged Donor–Acceptor sp 2 ‐Carbon‐Linked 2D Conjugated Polymers as Photocathodes for Water Reduction
Author(s) -
Xu Shunqi,
Sun Hanjun,
Addicoat Matthew,
Biswal Bishnu P.,
He Fan,
Park SangWook,
Paasch Silvia,
Zhang Tao,
Sheng Wenbo,
Brunner Eike,
Hou Yang,
Richter Marcus,
Feng Xinliang
Publication year - 2021
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.202006274
Subject(s) - materials science , homo/lumo , thiophene , conjugated system , density functional theory , water splitting , photochemistry , photocurrent , acceptor , polymer , photocatalysis , chemistry , computational chemistry , optoelectronics , organic chemistry , molecule , catalysis , physics , composite material , condensed matter physics
Photoelectrochemical (PEC) water reduction, converting solar energy into environmentally friendly hydrogen fuel, requires delicate design and synthesis of semiconductors with appropriate bandgaps, suitable energy levels of the frontier orbitals, and high intrinsic charge mobility. In this work, the synthesis of a novel bithiophene‐bridged donor–acceptor‐based 2D sp 2 ‐carbon‐linked conjugated polymer (2D CCP) is demonstrated. The Knoevenagel polymerization between the electron‐accepting building block 2,3,8,9,14,15‐hexa(4‐formylphenyl) diquinoxalino[2,3‐a:2′,3′‐c]phenazine (HATN‐6CHO) and the first electron‐donating linker 2,2′‐([2,2′‐bithiophene]‐5,5′‐diyl)diacetonitrile (ThDAN) provides the 2D CCP‐HATNThDAN (2D CCP‐Th). Compared with the corresponding biphenyl‐bridged 2D CCP‐HATN‐BDAN (2D CCP‐BD), the bithiophene‐based 2D CCP‐Th exhibits a wide light‐harvesting range (up to 674 nm), a optical energy gap (2.04 eV), and highest energy occupied molecular orbital–lowest unoccupied molecular orbital distributions for facilitated charge transfer, which make 2D CCP‐Th a promising candidate for PEC water reduction. As a result, 2D CCP‐Th presents a superb H 2 ‐evolution photocurrent density up to ≈7.9 µA cm −2 at 0 V versus reversible hydrogen electrode, which is superior to the reported 2D covalent organic frameworks and most carbon nitride materials (0.09–6.0 µA cm −2 ). Density functional theory calculations identify the thiophene units and cyano substituents at the vinylene linkage as active sites for the evolution of H 2 .