Boosting acidic oxygen evolution reaction through morphology and structure collaborative modulation of iridium-based catalysts

Abstract

The kinetically sluggish oxygen evolution reaction (OER) is a major bottleneck restricting the proton-exchange membrane water electrolysis (PEMWEs) for sustainable hydrogen generation. Nevertheless, further boosting OER catalytic performance still faces considerable challenges. Moreover, chlorine impurities are frequently incorporated during catalyst fabrication, which compromises the goal of green‑hydrogen production. Herein, we prepared several Iridium-based catalysts via a chlorine-free two step mixed drying and calcination method. The incorporation of NaNO₃, KNO₃ and CsNO₃ realized the collaborative modulation of structure and morphology. X-ray photoelectron spectroscopy (XPS) revealed that treatment with CsNO₃ yields a reduced iridium oxidation state and enhanced electron density at Ir active sites. Electrochemical tests confirmed notably reduced OER overpotentials (η) for catalysts modified with CsNO₃ (259.3 mV) and KNO₃ (264.7 mV) vs. reversible hydrogen electrode (RHE) at 10 mA cm⁻². Furthermore, the CsNO₃-modified catalyst exhibited outstanding 20 h stability in acidic media. We attribute the superior OER activity and stability of the CsNO₃-modified catalyst to the synergistic contributions of its distinctive nanorod morphology, unique new crystal structure (like K_0.25IrO₂), and enhanced electron density at Ir active sites. This study proposed a chlorine-free synthetic strategy that effectively enhances both electrocatalytic activity and durability, which promotes the development of high efficiency and sustainable PEM electrolysis technologies.