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DOE OSTI · 1838123

Increasing Iridium Oxide Activity for the Oxygen Evolution Reaction with Hafnium Modification

Zhao, Fang·Wen, Bo·Niu, Wenhan·Chen, Zhu·Yan, Chao·Selloni, Annabella·Tully, Christopher G.·Yang, Xiaofang·Koel, Bruce E.
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Abstract

Synthesis and implementation of highly active, stable, and affordable electrocatalysts for the oxygen evolution reaction (OER) is a major challenge in developing energy efficient and economically viable energy conversion devices such as electrolyzers, rechargeable metal-air batteries, and regenerative fuel cells. The current benchmark electrocatalyst for OER is based on iridium oxide (IrO x ) due to its superior performance and excellent stability. However, large scale applications using IrO x are impractical due to its low abundance and high cost. In this work, we report a highly active hafnium-modified iridium oxide (IrHf x O y ) electrocatalyst for OER. The IrHf x O y electrocatalyst demonstrated ten times higher activity in alkaline conditions (pH = 11) and four times higher activity in acid conditions (pH = 1) than a IrO x electrocatalyst. The highest intrinsic mass activity of the IrHf x O y catalyst in acid conditions was calculated as 6950 A gIrO x -1 at an overpotential (η) of 0.3 V. Combined studies utilizing operando surface enhanced Raman spectroscopy (SERS) and DFT calculations revealed that the active sites for OER are the Ir-O species for both IrO x and IrHf x O y catalysts. The presence of Hf sites leads to more negative charge states on nearby O sites, and shortening the bond lengths of Ir-O, and lowering free energies for OER intermediates to accelerate the OER process.

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRYHafniumHigh activityIridium oxideLow costOxygen evolution reaction

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Zhao, Fang, Wen, Bo, Niu, Wenhan, Chen, Zhu, Yan, Chao, Selloni, Annabella, Tully, Christopher G., Yang, Xiaofang, Koel, Bruce E.. 2021-09-01. Increasing Iridium Oxide Activity for the Oxygen Evolution Reaction with Hafnium Modification. https://doi.org/10.1021/jacs.1c03473

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