468008 Exploring Possible Active Sites for IrOx/SrIrO3, a Highly Active Oxygen Evolution Catalyst

Wednesday, November 16, 2016: 10:35 AM
Franciscan D (Hilton San Francisco Union Square)
Linsey C. Seitz1, Colin Dickens1, Kazunori Nishio2, Yasuyuki Hikita2, Joseph H. Montoya1, Andrew Doyle1, Charlotte Kirk1, Aleksandra Vojvodic3, Harold Y. Hwang2, Jens K. Nørskov4 and Thomas F. Jaramillo1, (1)Chemical Engineering, Stanford University, Stanford, CA, (2)Applied Physics, Stanford University, Stanford, CA, (3)SLAC National Accelerator Laboratory/Stanford University, Menlo Park, CA, (4)SUNCAT Center for Interface Science, Stanford University and SLAC National Laboratory, Stanford, CA

The Oxygen Evolution Reaction (OER) plays a key role in the renewable production of fuels and chemicals and is a source of inefficiency due to its sluggish kinetics. In addition to possessing high activity, OER catalysts must be stable for thousands of hours under operation. This is particularly challenging at the acidic conditions present in proton-exchange membrane electrolyzers. Currently, only Ir-based catalysts are practically stable for these applications,1 and improving the intrinsic activity of these catalysts provides a pathway to decreasing Ir usage. We have discovered a novel catalyst that forms in-situ as Sr leaches from SrIrO3 surface layers, leaving behind a remarkably active and acid-stable IrOx film with multiple orders of magnitude improvement over rutile IrO2 and RuO2.2

Herein, we use Density Functional Theory calculations to propose an explanation of the exceptional observed OER activity. We find the nominally prepared SrIrO3 perovskite to be thermodynamically unstable relative to aqueous Sr2+ and propose possible Sr-deficient overlayer structures that may form with electrochemical testing. Through a combination of lattice matching and ab initio molecular dynamics, we arrive at anatase IrO2 and IrOoverlayers that possess active sites at the peak of the theoretical activity volcano.

1C. C. L. McCrory, S. Jung, J. C. Peters, T. F. Jaramillo (2013). Benchmarking Heterogeneous Electrocatalysts for the Oxygen Evolution Reaction. Journal of the American Chemical Society, 135(45), 16977–16987. http://doi.org/10.1021/ja407115p

2L. C. Seitz, C. F. Dickens, K. Nishio, Y. Hikita, J. Montoya, A. Doyle, C. Kirk, A. Vojvodic, H. Y. Hwang, J. K. Norskov, T. F. Jaramillo (2016). A Highly Active and Stable SrIrO3/IrOx Catalyst for the Oxygen Evolution Reaction. In Review.

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