A Bio‐inspired Cu₄O₄ Cubane: Effective Molecular Catalysts for Electrocatalytic Water Oxidation in Aqueous Solution

Abstract

Inspired by the cubic Mn CaO cluster of natural oxygen-evolving complex in Photosystem II, tetrametallic molecular water oxidation catalysts, especially M O cubane-like clusters (M=transition metals), have aroused great interest in developing highly active and robust catalysts for water oxidation. Among these M O clusters, however, copper-based molecular catalysts are poorly understood. Now, bio-inspired Cu O cubanes are presented as effective molecular catalysts for electrocatalytic water oxidation in aqueous solution (pH 12). The exceptional catalytic activity is manifested with a turnover frequency (TOF) of 267 s for [(L -Cu) ] at 1.70 V and 105 s for [(L -Cu) ] at 1.56 V. Electrochemical and spectroscopic study revealed a successive two-electron transfer process in the Cu O cubanes to form high-valent Cu and Cu O intermediates during the catalysis.

Molecular Engineering of a 3D Self‐Supported Electrode for Oxygen Electrocatalysis in Neutral Media

“…Molecular coordination complexes have received increasing interest recently as OER and ORR electrocatalysts . Apart from the high activity, the structure of molecular catalysts can be determined and tuned.…”

Recent Advances in First‐Row Transition Metal Clusters for Photocatalytic Water Splitting

“…Copper was the first metal discovered and relatively abundant in nature with cheap expense. However, Cu‐based cubane cluster is rarely explored, and only one example of a Cu 4 O 4 cubane has been used as a catalyst for electrocatalytic water oxidation in 2018 . Subsequently, an octanuclear Cu(II) cluster [Cu 8 (dpk⋅OH) 8 (OAc) 4 ](ClO 4 ) 4 (dpk⋅OH=the monoanion of the hydrate) was reported by Ding's group.…”

Nature-inspired electrocatalysts and devices for energy conversion

“…[219][220][221][222] This complex has a sophisticated structure, in which a Mn 3 CaO 4 heterocubane is tethered to a fourth manganese ion via a m-oxo bridge and a corner oxo-attachment. [223][224][225] Even though the oxygen-evolving complex is still not fully understood at mechanistic level, metal-based clusters with cubane cores have already been synthesized as efficient catalysts for oxygen evolution reaction, imitating the Mn 4 CaO 5 active site of photosystem II. 221,224,[226][227][228] To improve the design of these bio-imitating electrocatalysts, fundamental understanding of the OER mechanism by oxygenic multi-metallic clusters is required, along with a significant improvement of their stability under the harsh oxidizing conditions of OER.…”

“…[223][224][225] Even though the oxygen-evolving complex is still not fully understood at mechanistic level, metal-based clusters with cubane cores have already been synthesized as efficient catalysts for oxygen evolution reaction, imitating the Mn 4 CaO 5 active site of photosystem II. 221,224,[226][227][228] To improve the design of these bio-imitating electrocatalysts, fundamental understanding of the OER mechanism by oxygenic multi-metallic clusters is required, along with a significant improvement of their stability under the harsh oxidizing conditions of OER. 229,231,232 The approach that nature utilizes to circumvent the oxidative degradation of photosystem II by continuously replacing and repairing the damaged protein subunit 220,229 in its structure cannot be applied in these artificial electrocatalysts.…”