Mixed-Metal Nickel–Iron\nOxide Aerogels for\nOxygen Evolution Reaction

Abstract

Alkaline\nelectrolyte membrane electrolyzers are a promising technology\nto efficiently produce clean hydrogen without the use of critical\nraw materials. At the heart of these electrolyzers are the electrocatalysts,\nwhich facilitate the cathodic and anodic reactions, with the latter\noxygen evolution reaction (OER) being the most sluggish. In recent\nyears, aerogels have become a very well-studied class of materials\ndue to their unique properties, including very high surface area.\nUntil now, aerogels have not been used to catalyze the OER by themselves\nbut were mainly considered catalyst supports. Here, mixed-metal nickel–iron\noxide aerogels were synthesized with a modified epoxide route synthesis\nand tested as OER catalysts. Depending on the Ni/Fe ratio, they show\nvery high catalytic activity and low overpotential to reach 10 mA\ncm^–2 (at η = 380 mV). This activity is beyond\nthat of the existing state-of-the-art platinum group metal-free OER\ncatalysts.