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Homogeneous Electrochemical Water Oxidation at Neutral pH by Water‐Soluble Ni II Complexes Bearing Redox Non‐innocent Tetraamido Macrocyclic Ligands
Author(s) -
Lee Husileng,
Wu Xiujuan,
Sun Licheng
Publication year - 2020
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.202000153
Subject(s) - redox , chemistry , electrochemistry , homogeneous , water soluble , inorganic chemistry , oxidation reduction , organic chemistry , electrode , biochemistry , physics , thermodynamics
Water oxidation is the bottleneck reaction in artificial photosynthesis. Exploring highly active and stable molecular water oxidation catalysts (WOCs) is still a great challenge. In this study, a water‐soluble Ni II complex bearing a redox non‐innocent tetraamido macrocyclic ligand (TAML) is found to be an efficient electrocatalyst for water oxidation in neutral potassium phosphate buffer. Controlled‐potential electrolysis experiments show that it can sustain at a steady current of approximately 0.2 mA cm −2 for >7 h at 1.75 V versus normal hydrogen electrode (NHE) without the formation of NiO x . Electrochemical and spectroelectrochemical tests show that the redox‐active ligand, as well as HPO 4 2− in the buffer, participate in the catalytic cycle. More importantly, catalytically active intermediate [Ni III (TAML 2− )−O . ] is formed via several proton‐coupled electron transfer processes and reacts with H 2 O with the assistance of base to release molecular oxygen. Thus, the employment of redox non‐innocent ligands is a useful strategy for designing effective molecular WOCs.