A highly dispersed amorphous iridium nanoclusters electrocatalyst synthesized at a quasi-room temperature for efficient oxygen evolution reaction

The water-splitting by proton-exchange-membrane (PEM) electrolyser is a highly appealing technology for hydrogen (H2) production. However, oxygen evolution reaction (OER) at anode of PEM electrolyser requires expensive and scarce iridium (Ir) catalysts to overcome its sluggish kinetics. Therefore, minimizing the amount of Ir used in OER electrocatalysts is critical for commercial application of PEM electrolyser. Herein, we report a flexible one-pot pathway to prepare carbon supported amorphous Ir nanoclusters (NCs) with low-Ir-loading (5.1 wt% Ir) via high-pressure hydrogen (1 MPa) reducing Ir(IV) precursors at a quasi-room temperature (50celcius). The obtained amorphous Ir NCs catalyst shows a high performance for OER in an acidic electrolyte with a overpotential of 290 mV and Tafel slope of 55 mV/dec, superior to those of crystalline Ir nanoparticles (NPs) and commercial Ir catalysts (340 mV; 77 mV/dec). We find that the high OER activity is related to amorphous IrOx formed on the Ir NCs surface. When Ir NCs was used as the anodic catalyst, the current density of the electrolyzer reached 30 mA cm-2 only requiring a cell voltage of 1.56 V. This work demonstrates that Ir NCs catalyst exhibits a promising application in practical overall water splitting for H2 production.