期刊
ACS CATALYSIS
卷 6, 期 11, 页码 7340-7349出版社
AMER CHEMICAL SOC
DOI: 10.1021/acscatal.6b02345
关键词
water oxidation catalyst; ruthenium water oxidation catalyst; density functional theory; surface-enhanced raman spectroscopy; online electrochemical mass spectrometry; cyclic voltammetry; UV-vis spectroscopy; pulse radiolysis
资金
- NINO Physical Sciences
- Netherlands Organization for Scientific Research (NINO)
- Higher Education Commission (HEC), Pakistan
- NWO-ECHO [713.011.002]
- BioSolar Cells open innovation consortium
- Dutch Ministry of Economic Affairs, Agriculture and Innovation [C1.9]
- Italian National Research Council (CNR, SolarFuelTandem) within the EUROCORES Programme EuroSolarFuels of the European Science Foundation (ESF)
- CNR [PM.P04.010]
- Progetto Bandiera N-CHEM
One of the key challenges in designing light-driven artificial photosynthesis devices is the optimization of the catalytic water oxidation process. For this optimization it is crucial to establish the catalytic mechanism and the intermediates of the catalytic cycle, yet a full description is often difficult to obtain using only experimental data. Here we consider a series of mononuclear ruthenium water oxidation catalysts of the form [Ru(cy)(L)(H2O)](2+) (cy = p-cymene, L = 2,2'-bipyridine and its derivatives). The proposed catalytic cycle and intermediates are examined using density functional theory (DFT), radiation chemistry, spectroscopic techniques, and electrochemistry to establish the water oxidation mechanism. The stability of the catalyst is investigated using online electrochemical mass spectrometry (OLEMS). The comparison between the calculated absorption spectra of the proposed intermediates with experimental spectra, as well as free energy calculations with electrochemical data, provides strong evidence for the proposed pathway: a water oxidation catalytic cycle involving four proton-coupled electron transfer (PCET) steps. The thermodynamic bottleneck is identified as the third PCET step, which involves O-O bond formation. The good agreement between the optical and thermodynamic data and DFT predictions further confirms the general applicability of this methodology as a powerful tool in the characterization of water oxidation catalysts and for the interpretation of experimental observables.
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