Optimizing Sputtered Iridium Electrocatalysts for Acidic Oxygen Evolution Using Design of Experiments

Iridium is considered the most effective electrocatalyst for the oxygen evolution reaction (OER) in acidic media. Often, iridium is mixed with cocatalysts or support materials to boost the OER performance and reduce the cost of water electrolyzers. To synthesize efficient iridium electrocatalysts, many studies vary either one or more fabrication parameters at a time without evaluating the potential interactions between them, which could improve the electrocatalysts’ overall performance. In this study, we examine the combined effects of iridium thickness, titanium adhesion layer thickness, annealing temperature, and annealing time on the performance of sputtered iridium electrocatalysts in sulfuric acid (H₂SO₄) through a factorial design of experiments (DoE). The DoE response analysis of our electrochemical data through the main, interaction, and standardized effects plots, with added experimental optimization of results, enabled the identification of a sputtered titanium-supported iridium electrocatalyst that operated continuously for 48 h in 1 M H₂SO₄ at 1.61 V vs RHE for a 10 mA/cm² current density. Our study shows how statistical analysis through factorial DoE can be used as a tool to improve the activity and stability of OER electrocatalysts in acidic media.