Enhanced alkaline hydrogen oxidation reaction using electrodeposited Ni-Ir alloy catalysts

The development of high-performance non/less-precious metal-based electrocatalysts for the hydrogen oxidation reaction (HOR) in anion exchange membrane fuel cells remains a challenge. Here, we report a bimetallic Ni-Ir catalyst fabricated using electrodeposition and optimized to improve its HOR performance in an alkaline environment. Bimetallic Ni-Ir catalysts of various compositions are electrochemically deposited on a glassy carbon (GC) disk electrode and their HOR activity in 0.1 M KOH is examined. It is found that Ni47Ir53 has the highest HOR activity of 2.09 and 2.28 mA cm-2 at 0.05 and 0.10 VRHE, respectively, outperforming a commercial Pt/C electrode. This improved performance is ascribed to the larger electrochemical surface area and the modification to the electronic structure via alloying. Electrochemical analysis revealed a low Tafel slope and a large exchange current density for Ni47Ir53, suggesting the presence of the Tafel-Volmer mechanism and a rapid Volmer reaction. The balanced H binding and OH binding with Ni47Ir53 is a significant contributor to the higher HOR activity. During accelerated durability testing, the oxidation state and electronic structure of the catalyst become more unfavorable for the HOR due to Ni dissolution, which supports the strategy of employing a dissolution-resistive alloying metal with Ir for alkaline HOR catalysts.