Abstract
AbstractPhotocatalytic water oxidation is a promising process for the production of solar fuels and the elucidation of factors that influence this process is of high significance. Thus, we have studied in detail light‐driven water oxidation with a trinuclear Ru(bda) (bda: 2,2’‐bipyridine‐6,6’‐dicarboxylate) macrocycle MC3 and its highly water soluble derivative m‐CH2NMe2‐MC3 using a series of ruthenium tris(bipyridine) complexes as photosensitizers under varied reaction conditions. Our investigations showed that the catalytic activities of these Ru macrocycles are significantly affected by the choice of photosensitizer (PS) and reaction media, in addition to buffer concentration, light intensity and concentration of the sensitizer. Our steady‐state and transient spectroscopic studies revealed that the photocatalytic performance of trinuclear Ru(bda) macrocycles is not limited by their intrinsic catalytic activities but rather by the efficiency of photogeneration of oxidant PS+ and its ability to act as an oxidizing agent to the catalysts as both are strongly dependent on the choice of photosensitizer and the amount of employed organic co‐solvent.
Highlights
Introduction application ofwater oxidation catalysts (WOCs) in solar fuels devices
The electrochemical properties of the photosensitizers PS1–3 were studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in phosphate buffered MeCN/H2O (1 : 1, v/v)
We have elucidated the effects of photosensitizers and reaction media on the efficiency of photocatalytic water oxidation with trinuclear Ru(bda) macrocycles MC3 and mCH2NMe2-MC3 using a series of ruthenium tris(bipyridine) photosensitizers and sodium persulfate as an electron acceptor
Summary
A key process in light-driven water oxidation is the activation of the WOC by oxidants generated by irradiation of a photosensitizer. The photocatalytic activities of homogeneous WOCs are generally studied by means of a three-component system comprising a photosensitizer (PS), a sacrificial electron acceptor and the catalyst. After activation of the PS to the excited state PS* by light [Eq (1)], the oxidant PS + is produced by one-electron transfer from PS* to the electron acceptor [Eq (2)] and PS is regenerated by oxidation of the WOC [Eq (5)]. Upon transfer of four electrons in a photocatalytic cycle, water is oxidized to molecular oxygen and four protons and four electrons are released [Eq (6)].[7] several PS and electron acceptor systems have been applied in photocatalytic water oxidation,[8] ruthenium tris(bipyridine) as PS and sodium persulfate as electron acceptor have become a standard combination for light-driven water oxidation by homogeneous
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