Surface Area and Electrocatalytic Properties of FeNi Nanoparticles for the Oxygen Evolution Reaction (OER)

Iron-nickel bimetallic electrocatalysts have recently emerged as some of the best candidates for the oxygen evolution reaction (OER) in alkaline electrolyte. Understanding the effects of composition and morphology of iron-nickel nanoparticles is crucial for optimization and enhanced electrocatalyst performance. Both physical surface area and electrochemical surface area (ECSA) are functions of morphology. In this study, four different iron-nickel nanoparticle catalysts were synthesized. The catalysts were varied based on morphology (alloy versus core-shell) and composition (low, medium, and high stabilizer concentration). Brunauer-Emmett-Teller (BET) surface area analysis was conducted on three of the synthesized iron-nickel nanoparticles using a physisorption analyzer while electrochemical impedance spectroscopy (EIS) was employed to quantify the ECSA by capacitance. Comparison of ECSA and BET results to electrocatalyst overpotential suggests both available surface area and nanoparticle morphology play roles in electrocatalytic activity. Additionally, compositional analysis by inductively coupled plasma mass spectroscopy (ICP-MS) suggests final nanoparticle composition is dependent on amount of stabilizing ligand added, with lower stabilizer concentrations resulting in less overall metal incorporation and larger deviations from theoretical compositions. This project holds ample future research opportunities to delineate the effects of stabilizers on final nanoparticle composition, physical surface area, electrochemical properties, and catalytic performance for OER. However, this work has helped to elucidate aspects of the property-performance relationship of this class of FeNi nanoparticles