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Nickel (II) tetrapyridyl complexes as electrocatalysts and precatalysts for water oxidation
Author(s) -
Li QiJun,
Ren YaJie,
Xie Qin,
Wu Min,
Feng HuaXing,
Zheng LiMei,
Zhang HuaXin,
Long JinQiao,
Wang TianShun
Publication year - 2020
Publication title -
applied organometallic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 71
eISSN - 1099-0739
pISSN - 0268-2605
DOI - 10.1002/aoc.5813
Subject(s) - overpotential , chemistry , nickel , catalysis , tafel equation , non blocking i/o , faraday efficiency , inorganic chemistry , nickel oxide , organometallic chemistry , electrochemistry , organic chemistry , electrode
Two nickel complexes, [Ni(tpen)](ClO 4 ) 2 .0.5CH 3 COCH 3 ( 1 ) and [Ni(tpbn)](ClO 4 ) 2 ( 2 ), of tetrapyridyl ligands N,N,N′,N′‐tetrakis(2‐pyridyl‐methyl)‐1,2‐ethanediamine (tpen) and N,N,N′,N′‐tetrakis(2‐pyridyl‐methyl)‐1,4‐butanediamine (tpbn) were prepared and their catalysis for water oxidation reaction (WOR) studied. In 0.1 M phosphate buffer solution (PBS) of pH 8.0, complex 1 is a homogeneous molecular catalyst with an overpotential of ~440 mV and a Faradaic efficiency of 89%. At pH ≥ 9.0, complex 1 degraded gradually during the catalytic process and formed NiO x composite (nickel oxide with general formula Ni x O y H z ) active for WOR. In contrast, complex 2 deteriorated under measured conditions (pH 8.0–12.0) and formed NiO x composite active for WOR. The NiO x composite derived from 1 in 0.1 M PBS at pH 11.0 showed an activity with an overpotential of ~500 mV, a Tafel slope of ~90 mV/decade and a Faradaic efficiency of 97%. Mechanisms were proposed for water oxidation catalyzed by 1 and 2 . This work revealed that the catalytic activity of the nickel complexes was related to the flexibility of the tetrapyridyl ligands and the adaptability of the coordination sphere of the nickel(II) center.