Control over Electrochemical Water Oxidation Catalysis by Preorganization of Molecular Ruthenium Catalysts in Self‐Assembled Nanospheres

Abstract

Oxygen formation through water oxidation catalysis is a key reaction in the context of fuel generation from renewable energies. The number of homogeneous catalysts that catalyze water oxidation at high rate with low overpotential is limited. Ruthenium complexes can be particularly active, especially if they facilitate a dinuclear pathway for oxygen bond formation step. A supramolecular encapsulation strategy is reported that involves preorganization of dilute solutions (10−5 m) of ruthenium complexes to yield high local catalyst concentrations (up to 0.54 m). The preorganization strategy enhances the water oxidation rate by two‐orders of magnitude to 125 s−1, as it facilitates the diffusion‐controlled rate‐limiting dinuclear coupling step. Moreover, it modulates reaction rates, enabling comprehensive elucidation of electrocatalytic reaction mechanisms.

Amphiphilic Oxo-Bridged Ruthenium “Green Dimer” for Water Oxidation

“…Surprisingly, the O-O bond formation pathways altered from radical coupling pathway to water nucleophilic attack when monomer 1 was replaced by dimer 2. The kinetic isotope effect (KIE) of 1 at different concentration was calculated as 1.19, in agreement with the previously established radical coupling pathway for O-O bond formation of Ru(bda) catalysts ( Figure 4C), whereas the O-O bond formation of 2 with a KIE of 2.18 ( Figure 4D) is similar to the famous blue dimer for O-O bond formation via water nucleophilic attack (Schulze et al, 2016;Shaffer et al, 2016;Khan et al, 2015;Yu et al, 2018).…”

Artificial photosynthesis: opportunities and challenges of molecular catalysts

“…143 Introduction of halogen substituents into the p-extended axial ligand further improved the catalytic activity of the Ru-bda catalysts, complex 16 with record TOF 4 1000 s À1 and complex 17 with record TON 4 100 000. To obtain higher catalytic activity, based on the bimolecular I2M mechanism of Ru-bda catalysts, various strategies have been tested to enhance the intermolecular interaction [167][168][169][170] or to create facile intramolecular reactions by linking two or more Ru-bda units, 171,172 e.g., complex 18.…”

Boosting H2 Generation Coupled with Selective Oxidation of Methanol into Value‐Added Chemical over Cobalt Hydroxide@Hydroxysulfide Nanosheets Electrocatalysts

“…Hydrogen, as a promising clean and renewable energy source with high calorific value and no emission of harmful substances in the process of using, is receiving a considerable attention than ever before. Electrocatalytic water splitting for hydrogen production powered by sustainable electricity has been regarded as an economical and environment‐friendly approach . In general, the overall water electrolysis consists of two half reactions—hydrogen evolution reaction (HER) at the cathode and oxygen evolution reaction (OER) at the anode.…”