Schedule Nov 06, 2009
Solar Hydrogen -- Theoretical Modeling of Photocatalytic Water Oxidation
Philip Allen (SUNY/BNL)

Department of Physics and Astronomy SUNY Stony Brook and Center for Functional Nanomaterials Brookhaven National Laboratory

This seminar reports work by a consortium called SWaSSiT (solar water splitting simulation team) involving Stony Brook and Brookhaven National Laboratory. The surface of the semiconductor alloy GaN/ZnO appears to be a good catalyst for water oxidation, using electronic excitations from solar photoexcitation in the interior of the same alloy. The overall process is 4hf + 2H2O → 2H2 + O2. The photons create electrons and holes (4hf → 4H+ +4e-). The electrochemistry takes place as two separate half-reactions. We focus on the more difficult oxidation process, 4h+ +2H2O → 2O2 + 4H+. The reduction process, 4e- + 4H+ → 2H2, requires a separate catalyst. Our density functional calculations suggest a route for the oxidation catalysis, with a candidate active site, thermodynamically favored reaction intermediates, and tentative identification of the rate-limiting process.

This work was a collaborative effort of the whole team (PBA, Marivi Fernandez-Serra, Mark Hybertsen, Li Li, James Muckerman, Xiao Shen, Yolanda Small, and Jue Wang. The largest contribution is from Xiao Shen, and was presented to Stony Brook University as a PhD thesis, awarded August 2009. Shen is now post-doc at Vanderbilt University.

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