title: Improving the efficiency of water splitting in dye-sensitized solar cells by using a biomimetic electron transfer mediator.
abstract: Photoelectrochemical water splitting directly converts solar energy to chemical energy stored in hydrogen, a high energy density fuel. Although water splitting using semiconductor photoelectrodes has been studied for more than 40 years, it has only recently been demonstrated using dye-sensitized electrodes. The quantum yield for water splitting in these dye-based systems has, so far, been very low because the charge recombination reaction is faster than the catalytic four-electron oxidation of water to oxygen. We show here that the quantum yield is more than doubled by incorporating an electron transfer mediator that is mimetic of the tyrosine-histidine mediator in Photosystem II. The mediator molecule is covalently bound to the water oxidation catalyst, a colloidal iridium oxide particle, and is coadsorbed onto a porous titanium dioxide electrode with a Ruthenium polypyridyl sensitizer. As in the natural photosynthetic system, this molecule mediates electron transfer between a relatively slow metal oxide catalyst that oxidizes water on the millisecond timescale and a dye molecule that is oxidized in a fast light-induced electron transfer reaction. The presence of the mediator molecule in the system results in photoelectrochemical water splitting with an internal quantum efficiency of approximately 2.3% using blue light.
authors.affiliation: Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Yixin
authors.initials: Y
authors.lastname: Zhao
authors.forename: John R
authors.initials: JR
authors.lastname: Swierk
authors.forename: Jackson D
authors.initials: JD
authors.lastname: Megiatto
authors.forename: Benjamin
authors.initials: B
authors.lastname: Sherman
authors.forename: W Justin
authors.initials: WJ
authors.lastname: Youngblood
authors.forename: Dongdong
authors.initials: D
authors.lastname: Qin
authors.forename: Deanna M
authors.initials: DM
authors.lastname: Lentz
authors.forename: Ana L
authors.initials: AL
authors.lastname: Moore
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Moore
authors.forename: Devens
authors.initials: D
authors.lastname: Gust
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Mallouk
mesh_terms: D040761:Biomimetic Materials / Q000737:chemistry*; D002384:Catalysis; D004396:Coloring Agents / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D045332:Photosystem II Protein Complex / Q000737:chemistry*; D012993:Solar Energy; D014867:Water / Q000737:chemistry*
chemical_list: D004396:Coloring Agents; D045332:Photosystem II Protein Complex; D014867:Water; D006859:Hydrogen; D010100:Oxygen