Hybrid Ir/TiO₂ Catalysts for PEM Water Electrolysis: Influence of Composition and Preparation Strategy on OER Performance

Proton exchange membrane water electrolysis (PEMWE) is a promising technology for sustainable green hydrogen production. However, the anodic oxygen evolution reaction (OER) still relies on scarce and high-cost iridium-based catalysts. In this context, the present work investigates hybrid catalysts based on mixtures of commercial Ir black and the less explored brookite-type TiO₂ phase, with Ir/TiO₂ mass ratios of 75/25, 50/50, and 25/75.

The catalysts are prepared by ultrasound-assisted mixing or thermal oxidation in air (300–600 °C) to evaluate the influence of the preparation strategy on their physicochemical properties and electrocatalytic performance toward the OER. Structural and surface characterization is carried out by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS), and scanning electron microscopy coupled with EDS (SEM-EDS). Electrochemical performance is evaluated by cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (CA).

Preliminary results for the ultrasound-prepared catalysts show that the Ir/TiO₂ 75/25 composition exhibits a particle size distribution and mass activity comparable to commercial Ir black (122.9 and 124.2 mA mgIr⁻¹, respectively). Moreover, chronoamperometric stability tests reveal a lower current density decay after 2 h at 1.5 V, decreasing from 1.125 to 1.073 mA cm⁻², compared with commercial Ir black (from 1.141 to 0.784 mA cm⁻²). The results suggest that the controlled incorporation of TiO₂ preserves the electrocatalytic activity while improving the electrochemical stability of the catalyst.

Consequently, the Ir/TiO₂ 75/25 composition was identified as the most promising formulation and selected as the reference catalyst for investigating the influence of thermal oxidation on catalyst performance, providing valuable insights for the development of more sustainable and economically viable anodic catalysts for PEM water electrolysis.