Electron transfer water splitting

While for a solar water splitting cell, light is directly absorbed by the semiconductor electrode (anode or cathode). The separation of electron-hole pairs is achieved in the built-in electric field near the semiconductor surface. The electric field is formed due to the charge transfer between the semiconductor electrode and the electrolyte as schematically shown in Fig. 17.5(b) [28]. Take an n-type semiconductor electrode for example... 

The reaction requires a sensitizer because water itself does not absorb above 200 nm. Transition-metal complexes exhibiting photoredox properties are useful as sensitizers for this reaction. The main problem, however, is that most transition-metal complexes involve one electron transfer per photon absorbed, whereas the water-splitting reaction... 

Based on the EPR, ENDOR, ESEEM and some other spectroscopic results models for Yz function in PS II have been developed (see references 385, 386 for recent reviews). There seems to be consensus that this amino acid is involved in proton-coupled electron-transfer. As proton acceptor His (Dl-190) was identified which is also found to be close to Yz in the recent X-ray structure.19 The postulated direct involvement of Yz in the water splitting process as a hydrogen atom abstractor or in separate or coupled proton/electron-transfer is still controversially discussed.385 386... 

Figure 17.2 illustrates our model for splitting water by solar energy. I" is important that all the redox reactions involved in thf system be reversible. The quinone compound in the organic solvent combines the two photocatalytic reactions, and its function can be compared to the electron relaying molecules in thylakoid membranes of chloroplasts. Electron transfer reactions via quinone compouncs in artificia systems have been studied as a model of photosynthesis22-23 and in an electrochemical system for acid concentration.24 ... 

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