Improving the efficiency of water splitting in dye-sensitized solar cells by using a biomimetic electron transfer mediator

Yixin Zhao, John R. Swierk, Jackson D. Megiatto, Benjamin Sherman, W. Justin Youngblood, Dongdong Qin, Deanna M. Lentz, Ana L. Moore, Thomas A. Moore, Devens Gust, Thomas E. Mallouk

Research output: Contribution to journalArticlepeer-review

274 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)15612-15616
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number39
StatePublished - Sep 25 2012

All Science Journal Classification (ASJC) codes

  • General


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