Water splitting configurations

Photocatalytic Water Splitting Under Visible Light Concept and Catalysts Development Ajay K. Ray, Photocatalytic Reactor Configurations for Water Purification Experimentation and... 

R.M. Navarro, F. del Valle, J.A. Villoria de la Mano, M.C. Alvarez-Galva n, and J.L.G. Fierro, Photocatalytic Water Splitting Under Visible Light Concept and Catalysts Development Ajay K. Ray, Photocatalytic Reactor Configurations for Water Purification Experimentation and Modeling... 

Fig. 1. Alternate configurations varying the number of photo harvesting units and electrolysis units for solar water splitting.3 The photoconverter in the first system generates the requisite water electrolysis voltage and in the second system generates twice that voltage, while the photoconverter in the third and fourth units generate respectively only half or a third this...

Photochemical Diodes and Twin-Photosystem Configurations for Water Splitting... 

Saygin and HT Witt (1975) Optical characterization of intermediates in the water-splitting enzyme system of photosynthesis-possible states and configuration of manganese and water. Biochim Biophys Acta 893 452-469... 

Fig. 2. (A) Flash-induced absorbance changes at 367 nm in PS-II particles isolated from Synechococcus at pH 7 and in the presence of 2X10 M silicomolybdate, (B) Spectra produced by each of four consecutive flashes in PS-II particles containing silicomolybdate. Figure source Saygin and Witt (1987) Optical characterization of intermediates in the water-splitting enzyme system of photosynthesis - possible slates and configuration of manganese and water. Biochim Biophys Acta 893 456, 457.

It is important to determine the conductivity and flat-band potential ( ft) of a photoelectrode before carrying out any photoelectrochemical experiments. These properties help to elucidate the band structure of a semiconductor which ultimately determines its ability to drive efficient water splitting. Photoanodes (n-type conductivity) drive the oxygen evolution reaction (OER) at the electrode-electrolyte interface, while photocathodes (p-type conductivity) drive the hydrogen evolution reaction (HER). The conductivity type is determined from the direction of the shift in the open circuit potential upon illumination. Illuminating the electrode surface will shift the Fermi level of the bulk (measured potential) towards more anodic potentials for a p-type material and towards more cathodic potentials for a n-type material. The conductivity type is also used to determine the potential ranges for three-electrode j-V measurements (see section Three-Electrode J-V and Photocurrent Onset ) and type of suitable electrolyte solutions (see section Cell Setup and Connections for Three- and Two-Electrode Configurations ) used for the electrochemical analyses. 

In order to achieve water splitting, some PEC devices require a potential bias. In some standalone configurations, such as the tandem hybrid device, such a bias can be provided internally by a photovoltaic junction stacked in series with the PEC junction. The determination of the saturated photocurrent density achievable by a PEC material, as well as the bias required to achieve this value, is crucial in identifying possible integration schemes for the material of interest. 

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