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In this study, we highlight the impact of catalyst geometry on the formation of O−O bonds in Cu2 and Fe2 catalysts. A series of Cu2 complexes with diverse linkers are designed as electrocatalysts for water oxidation. Interestingly, the catalytic performance of these Cu2 complexes is enhanced as their molecular skeletons become more rigid, which contrasts with the behavior observed in our previous investigation with Fe2 analogs. Moreover, mechanistic studies reveal that the reactivity of the bridging O atom results in distinct pathways for O−O bond formation in Cu2 and Fe2 catalysts. In Cu2 systems, the coupling takes place between a terminal CuIII−OH and a bridging μ−O⋅ radical. Whereas in Fe2 systems, it involves the coupling of two terminal Fe–oxo entities. Furthermore, an in‐depth structure–activity analysis uncovers the spatial geometric prerequisites for the coupling of the terminal OH with the bridging μ−O⋅ radical, ultimately leading to the O−O bond formation. Overall, this study emphasizes the critical role of precisely adjusting the spatial geometry of catalysts to align with the O−O bonding pathway. [ABSTRACT FROM AUTHOR]

We report herein the first nonheme CuFe oxygen reduction catalyst ([CuII(bpbp)(μ‐OAc)2FeIII]2+, CuFe−OAc), which serves as a functional model of cytochrome c oxidase and can catalyze oxygen reduction to water with a turnover frequency of 2.4×103 s−1 and selectivity of 96.0 % in the presence of Et3NH+. This performance significantly outcompetes its homobimetallic analogues (2.7 s−1 of CuCu−OAc with %H2O2 selectivity of 98.9 %, and inactive of FeFe−OAc) under the same conditions. Structure‐activity relationship studies, in combination with density functional theory calculation, show that the CuFe center efficiently mediates O−O bond cleavage via a CuII(μ‐η1 : η2‐O2)FeIII peroxo intermediate in which the peroxo ligand possesses distinctive coordinating and electronic character. Our work sheds light on the nature of Cu/Fe heterobimetallic cooperation in oxygen reduction catalysis and demonstrates the potential of this synergistic effect in the design of nonheme oxygen reduction catalysts. [ABSTRACT FROM AUTHOR]

We reported herein the development of heterobimetallic NiFe molecular platform to understand NiFe synergistic effect in water oxidation catalysis. Compared to homonuclear bimetallic compounds (NiNi and FeFe), NiFe complex possesses more remarkable catalytic water oxidation performance. Mechanistic studies suggest that this remarkable difference is attributed to the fact that NiFe synergy can effectively promote O−O bond formation. The generated NiIII(μ‐O)FeIV=O is the key intermediate and O−O bond was formed via intramolecular oxyl‐oxo coupling between bridged O radical and terminal FeIV=O moiety. [ABSTRACT FROM AUTHOR]

Water splitting is one of the most promising solutions for storing solar energy in a chemical bond. Water oxidation is still the bottleneck step because of its inherent difficulty and the limited understanding of the O−O bond formation mechanism. Molecular catalysts provide a platform for understanding this process in depth and have received wide attention since the first Ru‐based catalyst was reported in 1982. RuV=O is considered a key intermediate to initiate the O−O bond formation through either a water nucleophilic attack (WNA) pathway or a bimolecular coupling (I2M) pathway. Herein, we report a Ru‐based catalyst that displays water oxidation reactivity with RuIV=(O) with the help of a redox‐active ligand at pH 7.0. The results of electrochemical studies and DFT calculations disclose that ligand oxidation could significantly improve the reactivity of RuIV=O toward water oxidation. Under these conditions, sustained water oxidation catalysis occurs at reasonable rates with low overpotential (ca. 183 mV). [ABSTRACT FROM AUTHOR]

The complex CuII(Py3P) ( 1) is an electrocatalyst for water oxidation to dioxygen in H2PO4−/HPO42− buffered aqueous solutions. Controlled potential electrolysis experiments with 1 at pH 8.0 at an applied potential of 1.40 V versus the normal hydrogen electrode resulted in the formation of dioxygen (84 % Faradaic yield) through multiple catalyst turnovers with minimal catalyst deactivation. The results of an electrochemical kinetics study point to a single-site mechanism for water oxidation catalysis with involvement of phosphate buffer anions either through atom-proton transfer in a rate-limiting OO bond-forming step with HPO42− as the acceptor base or by concerted electron-proton transfer with electron transfer to the electrode and proton transfer to the HPO42− base. [ABSTRACT FROM AUTHOR]