Ultrafine iridium nanoparticles grown on sea urchin-like PdCu with boosted activity toward acidic oxygen evolution

Abstract

Proton exchange membrane water electrolyzers (PEMWEs) confront the grand challenge of sluggish kinetics of oxygen evolution reaction (OER). Herein, we present the synthesis of ultrafine 1–2 nm Ir particles on sea urchin-like PdCu (Ir0.58/Pd1.9Cu) via wet chemical reduction of PdCl42− and Cu2+, followed by simple displacement of PdHx by Ir3+ with the aid of HCOOH. Ir0.58/Pd1.9Cu exhibits an overpotential of 191 mV at 10 mA/cm2 superior to that of commercial Ir black (262 mV) toward acidic OER. The electrochemically active surface area of Ir0.58/Pd1.9Cu (850.6 m2/g) is much higher than that of commercial Ir black (411.9 m2/g), and should be a major contributor to the high OER activity. The electronic interaction between PdCu and Ir nanoparticles well tunes the electronic structure of Ir, possibly conferring Ir0.58/Pd1.9Cu with high activity. Furthermore, density functional theory reveals that the OER rate-determining step (∗O → ∗OOH) on Ir/PdCu has a lowered energy barrier of 0.33 eV compared with that of Ir, beneficial for the high OER activity. Additionally, Ir0.58/Pd1.9Cu demonstrates a reasonably good stability during 20 h of chronopotentiometry test, superior to that of commercial Ir black. Finally, the high OER activity of Ir0.58/Pd1.9Cu was verified in a PEMWE.