Nanostructured Layered\nLithium Iridates as Electrocatalysts\nfor Improved Oxygen Evolution Reaction

Abstract

We report for the first time the synthesis pathway of\nnanostructured\nlithium iridates in molten salts with tunable particle and crystal\nsizes. The structural analysis confirms that these materials are phase-pure,\nwith a layered α-Li₂IrO₃ structure and\na surface area 2 orders of magnitude higher than that of the materials\nobtained by traditional solid-state methodology. Improved OER activities\nwere obtained compared to the bulk counterpart, given the improved\nsurface area. Intriguingly, the electrocatalytic behavior of this\nnanoscaled α-Li₂IrO₃ significantly differs\nfrom the bulk counterpart. Such a different behavior may arise from\nthe small size of the synthesized materials; thus, surface reactions\nplay a key role. Additionally, the nanoscaled α-Li₂IrO₃ shows good chemical and structural stability; thus,\nnegligible deactivation was observed in KOH and H₂SO₄ electrolytes with low electrode catalyst loading during 24\nh of chronopotentiometry. Besides this stability, these materials\nshow enhanced iridium intrinsic activity with 336 and 181 A g_Ir^–1 in H₂SO₄ and KOH\nelectrolytes, respectively. This work shows how the design of high-temperature\ncolloidal synthesis yields nanoscaled materials with enhanced and\ndifferent electrocatalytic properties compared to bulk counterparts\nand pave the way to the design of electrocatalysts with enhanced mass\nactivity.