A New Catalyst for Splitting Water into Molecular

A New Catalyst for Splitting Water into Molecular Oxygen James M. Krier UC-Berkeley

Unique challenges ahead Energy = N (GDP/N)(E/GDP) Per person GDP Energy intensity Even with optimistic technological and conservation forecasts, the rapid economic growth in developing nations is predicted to double global energy needs by 2050 N. S. Lewis, D. G. Nocera, Proc. Natl. Acad. Sci. U. S. A. 103, 15729 (2006).

Power from the sun 2 H 2(g) + O 2(g) → 2 H 2 O(l) ∆H = -286 k. J/mol bcs. whfreeman. com/lehninger • Enough solar energy strikes the globe in one hour (4. 3 x 1020 J) to power all human activity for one year (4. 1 x 1020 J) • Photosynthesis by plants is an example of splitting water for energy storage N. S. Lewis, D. G. Nocera, Proc. Natl. Acad. Sci. U. S. A. 103, 15729 (2006).

The artificial plant The oxygen reaction is tricky in both systems N. S. Lewis, D. G. Nocera, Proc. Natl. Acad. Sci. U. S. A. 103, 15729 (2006).

Recent breakthrough e- e+ - 1. 29 V Conducting glass, such as indium tin oxide 0. 5 m. M Co(NO 3)2 0. 1 M KPi (potassium phosphate) SEM image Alternative: Kanan, M. W. & Nocera, D. G. Science 321, 1072– 1075 (2008). Film is 2: 1 as Co: Pi

Key features • Self-repair mechanism, in situ formation • Co 2+, Co 3+, Co 4+ species likely responsible for balancing different oxidation steps • Co 2+-HPO 42 - (aq) Co 3+-HPO 42 - (on electrode surface) • Composed of earth-abundant materials • Long lasting O 2 production at low overpotential, neutral p. H, room temperature/pressure • Drawbacks: large initial overpotential, not effective at high current Kanan, M. W. & Nocera, D. G. Science 321, 1072– 1075 (2008).

web. mit. edu/newsoffice/2008/oxygen-0731. html Your new house? Kanan, M. W. & Nocera, D. G. Science 321, 1072– 1075 (2008).

Links to additional reading… nature. com/nmat/journal/v 7/n 10/full/nmat 2284. html rsc. org/ej/CS/2009/b 802262 n. pdf sciencemag. org/cgi/reprint/321/5892/1072. pdf www. web. mit. edu/newsoffice/2008/oxygen-0731. html www. pnas. org/content/103/43/15729. abstract