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      Dynamics of photogenerated holes in undoped BiVO4 photoanodes for solar water oxidation

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          Abstract

          We use transient absorption spectroscopy and photoelectrochemical methods to study the dynamics of photogenerated holes in BiVO4 for solar water oxidation. The back electron/hole recombination is found to be slow and therefore competes with water oxidation, limiting water oxidation efficiency.

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          Most cited references 35

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          Efficient solar water splitting by enhanced charge separation in a bismuth vanadate-silicon tandem photoelectrode.

           M. Zeman,  L. Han,  Arno Smets (2012)
          Metal oxides are generally very stable in aqueous solutions and cheap, but their photochemical activity is usually limited by poor charge carrier separation. Here we show that this problem can be solved by introducing a gradient dopant concentration in the metal oxide film, thereby creating a distributed n(+)-n homojunction. This concept is demonstrated with a low-cost, spray-deposited and non-porous tungsten-doped bismuth vanadate photoanode in which carrier-separation efficiencies of up to 80% are achieved. By combining this state-of-the-art photoanode with an earth-abundant cobalt phosphate water-oxidation catalyst and a double- or single-junction amorphous Si solar cell in a tandem configuration, stable short-circuit water-splitting photocurrents of ~4 and 3 mA cm(-2), respectively, are achieved under 1 sun illumination. The 4 mA cm(-2) photocurrent corresponds to a solar-to-hydrogen efficiency of 4.9%, which is the highest efficiency yet reported for a stand-alone water-splitting device based on a metal oxide photoanode.
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            Accelerating materials development for photoelectrochemical hydrogen production: Standards for methods, definitions, and reporting protocols

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              Spatial separation of photogenerated electrons and holes among {010} and {110} crystal facets of BiVO4.

               Mingrun Li,  J Yang,  Z. Wang (2012)
              Charge separation is crucial for increasing the activity of semiconductor-based photocatalysts, especially in water splitting reactions. Here we show, using monoclinic bismuth vanadate crystal as a model photocatalyst, that efficient charge separation can be achieved on different crystal facets, as evidenced by the reduction reaction with photogenerated electrons and oxidation reaction with photogenerated holes, which take place separately on the {010} and {110} facets under photo-irradiation. Based on this finding, the reduction and oxidation cocatalysts are selectively deposited on the {010} and {110} facets respectively, resulting in much higher activity in both photocatalytic and photoelectrocatalytic water oxidation reactions, compared with the photocatalyst with randomly distributed cocatalysts. These results show that the photogenrated electrons and holes can be separated between the different facets of semiconductor crystals. This finding may be useful in semiconductor physics and chemistry to construct highly efficient solar energy conversion systems.
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                Author and article information

                Journal
                CSHCBM
                Chem. Sci.
                Chem. Sci.
                Royal Society of Chemistry (RSC)
                2041-6520
                2041-6539
                2014
                2014
                : 5
                : 8
                : 2964-2973
                Article
                10.1039/C4SC00469H
                © 2014
                Product
                Self URI (article page): http://xlink.rsc.org/?DOI=C4SC00469H

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