Molecular catalysis of water oxidation has been intensively
investigated,
but its mechanism is still not yet fully understood. This study aims
at capturing and identifying key short-lived intermediates directly
during the water oxidation catalyzed by a cobalt-tetraamido macrocyclic
ligand complex using a newly developed an in situ electrochemical
mass spectrometry (EC-MS) method. Two key ligand-centered-oxidation
intermediates, [(L2–)CoIIIOH] and [(L2–)CoIIIOOH], were directly observed for
the first time, and further confirmed by 18O-labeling and
collision-induced dissociation studies. These experimental results
further confirmed the rationality of the water nucleophilic attack
mechanism for the single-site water oxidation catalysis. This work
also demonstrated that such an in situ EC-MS method is a promising
analytical tool for redox catalytic processes, not only limited to
water oxidation.
Electrochemical mass spectrometry (EC-MS) is a powerful tool to capture and analyze the intermediates and products during electrochemical reactions. This hyphenated technique combines electrochemistry with mass spectrometry using specific apparatuses, which helps researchers study mechanisms of redox reactions by in situ detecting chemical composition changes. Recently, various EC-MS methods have been applied in a series of electrochemical reactions to reveal the mechanisms, mainly in the areas of electrochemical sensors, organic electrochemistry, and electrocatalysis. In this review, we intend to summarize the recent advances in real-time analysis of different types of electrochemical reactions by EC-MS and offer an outlook on the perspectives in these areas.
As one phase constituting of a liquid/liquid (L/L) interface, suitable organic solvents are of great significance for the study of electrochemistry at a L/L interface. In this work, the thermodynamic and kinetic parameters of simple ion transfer (IT) at the water/trifluorotoluene (W/TFT) interface were measured using micro-and nanopipettes voltammetry, respectively. In addition to the study of model ions, we have also explored some ions whose transfer potentials are close to the two ends of the potential window. Inspired by the work of the W/TFT interface, we also further developed two novel L/L interfaces and investigated various simple IT reactions based on the W/oand p-methylbenzotrifluoride (W/o-and p-MBTF) interfaces. The transfer potential and Gibbs energy of ITs across the W/o-and p-MBTF interface were determined by the analysis of the electrochemical voltametric curves. Special attention should be paid to that we can observe the IT peak or steady-state of tetraamyl ammonium (TAA + ) at W/o-and p-MBTF interfaces with no difficulty, which is rather challenging at other L/L interfaces. Compared to the classical W/1,2-dichloroethane (DCE) and W/ nitrobenzene (NB) interfaces, the W/TFT and its derivatives interfaces exhibit low toxicity, favourable stability, and wider potential windows, which can be better choices for replacing the traditional organic solvents in the electrochemical study at a L/L interface.
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