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Poly(1,4‐di(2‐thienyl))benzene Facilitating Complete Light‐Driven Water Splitting under Visible Light at High pH
Author(s) -
Oka Kouki,
Noguchi Kanako,
Suga Takeo,
Nishide Hiroyuki,
WintherJensen Bjorn
Publication year - 2019
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201803286
Subject(s) - water splitting , materials science , photochemistry , visible spectrum , thiophene , anode , polymerization , benzene , hydrogen , polymer , chemistry , photocatalysis , electrode , optoelectronics , catalysis , biochemistry , organic chemistry , composite material
The recent discovery that metal‐free polyterthiophene (PTTh) prepared by iodine‐vapor‐assisted polymerization (IVP) can catalyze the hydrogen evolution reaction (HER) when illuminated, and this light‐enhanced electrolysis expresses a non‐Nernstian relation with pH, provides the foundation for further improvement of the photovoltage of the reaction by engineering the band structure of the light‐absorbing polymer. Deviating from an all‐thiophene backbone, using poly(1,4‐di(2‐thienyl))benzene (PDTB) lowers the highest occupied molecular orbital level by ≈0.3 eV compared with polythiophene, and PDTB simultaneously maintains the photoelectrocatalytic properties without an all‐thiophene backbone, resulting in very high conversion rate of 600 mmol(H 2 ) h −1 g −1 at 0 V versus the reversible hydrogen electrode (RHE) at pH 11. PDTB shows the same non‐Nernstian behavior as PTTh with increasing onset potential (versus RHE) at higher pH, and the open circuit potential on PDTB under visible light reaches 1.4 V versus RHE at pH 12. The PDTB photocathode thus produces a photovoltage above the theoretical potential for the complete water‐splitting (1.229 V) and is indeed able to produce hydrogen in a one‐photon‐per‐electron light‐driven water splitting setup with MnO x as the anode at a rate of 6.4 mmol h −1 g PDTB −1 .