Nanostructured Layered Lithium Iridates as Electrocatalysts for Improved Oxygen Evolution Reaction

Abstract

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 α-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 α-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 α-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.