Nanostructured Layered Lithium Iridates as Electrocatalysts for Improved Oxygen Evolution Reaction

Abstract

[EN] We report for the first time the synthesis pathway of nanostructured lithium iridates in molten salts with tunable particle and crystal sizes. The structural analysis confirms that these materials are phase-pure, with a layered alpha- Li2IrO3 structure and a surface area 2 orders of magnitude higher than that of the materials obtained by traditional solid-state methodology. Improved OER activities were obtained compared to the bulk counterpart, given the improved surface area. Intriguingly, the electrocatalytic behavior of this nanoscaled alpha-Li2IrO3 significantly differs from the bulk counterpart. Such a different behavior may arise from the small size of the synthesized materials; thus, surface reactions play a key role. Additionally, the nanoscaled alpha-Li2IrO3 shows good chemical and structural stability; thus, negligible deactivation was observed in KOH and H2SO4 electrolytes with low electrode catalyst loading during 24 h of chronopotentiometry. Besides this stability, these materials show enhanced iridium intrinsic activity with 336 and 181 A gIr-1 in H2SO4 and KOH electrolytes, respectively. This work shows how the design of high-temperature colloidal synthesis yields nanoscaled materials with enhanced and different electrocatalytic properties compared to bulk counterparts and pave the way to the design of electrocatalysts with enhanced mass activity.