Solar Water Splitting Cells

Division of Chemistry and Chemical Engineering, 210 Noyes Laboratory, 127-72 California Institute of Technology, Pasadena, California 91125, USA.
Chemical Reviews (Impact Factor: 46.57). 11/2010; 110(11):6446-73. DOI: 10.1021/cr1002326
Source: PubMed


Water splitting cells with direct semiconductor/liquid contacts are attractive because they avoid significant fabrication and systems costs involved with the use of separate electrolyzers wired to p-n junction solar cells. Another attractive advantage of photoelectrochemical water splitting directly at the semiconductor surface is the ease with which an electric field can be created at a semiconductor/liquid junction. Water splitting cells require semiconductor materials that are able to support rapid charge transfer at a semiconductor/aqueous interface, that exhibit long-term stability, and that can efficiently harvest a large portion of the solar spectrum. In contrast to the use of a single band gap configuration (S2) to split water, the use of a dual band gap (D4) water splitting cell configuration, where the electric field is generated at a semiconductor liquid junction or through a buried junction, appears to be the most efficient and robust use of complementary light absorbing materials.

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    • "Electrolysis of water is a simple method to produce high-purity hydrogen and two half reactions are involved under acidic conditions: 4H þ þ 4e / 2H 2 (cathode reduction) and 2H 2 O / O 2 þ 4H þ þ 4e (anode oxidation). However, to make the hydrogen evolution reaction (HER) more energyefficient , an advanced electrocatalyst is required to drive high current density at low overpotential (h) [3]. Pt-group metals are the most active catalysts but suffer from high cost. "
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    • "Solar energy, one of clean and environmentally friendly energy mode, is drawing more and more attention to meet the increasing demands in this century12. As a promising method, the photoelectrochemical (PEC) water splitting into H2 and O2 on semiconductor photoanode, it offers a solution to harvest and store solar energy3456. Hematite (α-Fe2O3) is currently considered one of the most promising photoanode materials for water splitting due to a series of desirable properties, including adequate absorption from the visible light region in solar spectrum (bandgap between 2.0 and 2.2 eV), high theoretical photocurrents under 1.5 AM illumination, excellent stability in an aqueous environment, and abundant existence in nature4789. "
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    • "For example, in metal-assisted chemical (MAC) etching, electroless metal deposition onto Si substrate is most widely used to deposit catalyst layer, which functions as catalyst to provide holes to local region [9]. Another example is the deposition of a catalyst on photoelectrodes for solar water splitting [10]. "
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