Surface-engineered Ir/Au dendritic catalysts with minimal iridium loading for efficient alkaline oxygen evolution

Abstract

Electrochemical water splitting is a promising strategy for sustainable hydrogen production, yet the sluggish oxygen evolution reaction (OER) at the anode remains a major bottleneck. Here, we report the fabrication of a low-Ir-content electrocatalyst by anchoring sparse Ir atoms onto high-surface-area dendritic gold (Ir/Au-D) via a copper underpotential deposition (UPD) and redox replacement method. Structural characterization confirms the formation of a stable, highly dispersed Ir/Au surface interface without Ir aggregation. Electrocatalytic measurements demonstrate that Ir/Au-D achieves an overpotential of 301 mV at 10 mA cm⁻² in 1.0 M KOH, a low Tafel slope of 36 mV dec⁻¹, and a turnover frequency (TOF) of 3.03 s⁻¹ at 300 mV (vs. 1.23 V), outperforming Pt wire, Ir wire, and bare Au-D electrodes. Stability tests further reveal negligible performance decay over 20 hours of continuous operation. The enhanced OER activity is attributed to the electronic modulation of Ir atoms by the Au substrate and the synergistic effect at the Ir/Au interface, which promotes intermediate formation and product desorption. This hypothesis is experimentally supported by in situ surface-enhanced Raman spectroscopy (SERS), which reveals characteristic bands associated with Ir–O and O–O vibrations under applied potentials. This work provides an effective strategy for maximizing catalytic efficiency through minimal noble metal loading and stable interfacial engineering, offering insights for the design of next-generation low-metal-content OER catalysts.