Gao, J., Tan, S. X., Liu, Y., Liu, B., & Huang, K.-W. (2023). Revisiting the Activity Gap of Iridium Electrocatalysts for Acidic Water Oxidation. The Journal of Physical Chemistry Letters, 14(28), 6494–6505. https://doi.org/10.1021/acs.jpclett.3c01161
Abstract:
Iridium electrocatalyst has been extensively studied for acidic water oxidation reaction (2H2O → O2 + 4H+ + 4e–, also known as the oxygen evolution reaction, OER) in recent years, and much progress has been made regarding the structure-performance correlations and reaction mechanism. However, the activity of different iridium catalysts, such as amorphous, crystalline, and metallic ones, varies significantly, and there is no common explanation for the origin. Here four types of iridium catalysts were selected as models, including iridium oxide hydrate, rutile phase iridium oxide with good crystallinity, metallic iridium black, and iridium oxide nanoparticles. The structure of the catalysts was characterized by various techniques, and an active sites depth index is proposed to construct the structural model of the iridium catalysts. The intrinsic activity of the four iridium catalysts was measured and compared. The redox behavior of iridium catalysts and oxidation of hydrogen peroxide were applied to in-situ probe the adsorption energy of oxygen reaction intermediates (*OH, *O, and *OOH) on iridium catalysts under OER conditions. Structure-activity analysis suggested that the more optimal and broader distribution of adsorption energies on metallic iridium (iridium black), as well as its good conductivity, are the origin of its highest activity among the four different iridium catalysts. Rutile phase iridium oxide with good crystallinity shows the lowest activity due to its strongest and narrowest adsorption energy distribution compared with other catalysts. This work would provide an alternative route to design more active iridium catalysts for the water oxidation reaction.
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Funding Info:
This research / project is supported by the Public Utilities Board (PUB) - Competitive Funding for Water Research
Grant Reference no. : CWR 2101-0029
This research / project is supported by the A*STAR - Career Development Fund
Grant Reference no. : C210812029
This research / project is supported by the A*STAR - Central Research Fund
Grant Reference no. : SC22/22-11571U