A Bifunctional Nonprecious Metal Catalyst for Oxygen Reduction and Water Oxidation

TLDR

Oxygen electrochemistry is increasingly important for renewable energy technologies that convert between O₂ and H₂O. This study aims to develop active bifunctional catalysts for water oxidation and oxygen reduction. Inspired by the cubane‑like CaMn₄Oₓ in photosystem II, the authors investigated nanostructured manganese oxide surfaces as catalysts. Thin films of nanostructured Mn oxide were active for both oxygen reduction and water oxidation, matching the performance of platinum, ruthenium, and iridium catalysts, and exhibited Mn(III) oxidation states similar to those in the OEC.

Abstract

There is a growing interest in oxygen electrochemistry as conversions between O2 and H2O play an important role in a variety of renewable energy technologies. The goal of this work is to develop active bifunctional catalyst materials for water oxidation and oxygen reduction. Drawing inspiration from a cubane-like CaMn4Ox, the biological catalyst found in the oxygen evolving center (OEC) in photosystem II, nanostructured manganese oxide surfaces were investigated for these reactions. Thin films of nanostructured manganese oxide were found to be active for both oxygen reduction and water oxidation, with similar overall oxygen electrode activity to the best known precious metal nanoparticle catalysts: platinum, ruthenium, and iridium. Physical and chemical characterization of the nanostructured Mn oxide bifunctional catalyst reveals an oxidation state of Mn(III), akin to one of the most commonly observed Mn oxidation states found in the OEC.