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Improvement of Electrochemical Water Oxidation by Fine‐Tuning the Structure of Tetradentate N 4 Ligands of Molecular Copper Catalysts
Author(s) -
Shen Junyu,
Wang Mei,
Gao Jinsuo,
Han Hongxian,
Liu Hong,
Sun Licheng
Publication year - 2017
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201701458
Subject(s) - overpotential , electrochemistry , faraday efficiency , copper , catalysis , electrolysis , chemistry , cathode , inorganic chemistry , redox , organic chemistry , electrode , electrolyte
Two copper complexes, [( L1 )Cu(OH 2 )](BF 4 ) 2 [ 1 ; L1 = N , N ′‐dimethyl‐ N , N ′‐bis(pyridin‐2‐ylmethyl)‐1,2‐diaminoethane] and [( L2 )Cu(OH 2 )](BF 4 ) 2 [ 2 , L2 =2,7‐bis(2‐pyridyl)‐3,6‐diaza‐2,6‐octadiene], were prepared as molecular water oxidation catalysts. Complex 1 displayed an overpotential ( η ) of 1.07 V at 1 mA cm −2 and an observed rate constant ( k obs ) of 13.5 s −1 at η 1.0 V in pH 9.0 phosphate buffer solution, whereas 2 exhibited a significantly smaller η (0.70 V) to reach 1 mA cm −2 and a higher k obs (50.4 s −1 ) than 1 under identical test conditions. Additionally, 2 displayed better stability than 1 in controlled potential electrolysis experiments with a faradaic efficiency of 94 % for O 2 evolution at 1.58 V, when a casing tube was used for the Pt cathode. A possible mechanism for 1 ‐ and 2 ‐catalyzed O 2 evolution reactions is discussed based on the experimental evidence. These comparative results indicate that fine‐tuning the structures of tetradentate N 4 ligands can bring about significant change in the performance of copper complexes for electrochemical water oxidation.