Directed assembly of ultrasmall nitrogen coordinated Ir nanoparticles for enhanced electrocatalysis

Abstract

Iridium-based catalysts are state-of-the-art catalysts for oxygen evolution reaction (OER) under highly corrosive acidic condition. However, it remains challenges to simultaneously achieve enhanced activity and stability from Ir based OER catalyst. Herein, the amine molecules directed assembly method is used to coat of ultrasmall Ir nanoparticles (~1.3 nm) on carbon (Ir NP/C). The catalyst with ultralow loading of 13.5 ᶙgIr cm−2 exhibits 70 mV lower overpotential to reach a current density of 10 mA cm−2 and much longer lifetime than that of commercial IrO2 with high loading of 102 ᶙgIr cm−2. Experimental results suggest that the presence of a higher proportion of Ir-N on the top atomic layer of ultrasmall Ir nanoparticles, as evident from the X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) spectra of Ir NP/C, facilitated the enhanced performance. The findings could promote the understanding and developing of active Ir-based OER nanocatalysts with longer lifetime.