A Bifunctional Iron Nickel Catalyst for the Oxygen Evolution Reaction

The oxygen evolution reaction (OER) is a key process that enables the storage of renewable energies in the form of chemical fuels. Although numerous transition metal oxides have been explored as OER catalysts, the scaling relationship of the binding energies of various surface-bound intermediates imposes a limit on the maximum activity of these oxides. While previous computational studies have suggested bifunctional catalysts might be capable of overcoming this limit, stable and non-precious catalysts of this type remain elusive. Here, we describe a catalyst that exhibits activity significantly higher than current state-of-the-art catalysts that operate in alkaline solutions, including the benchmark nickel iron oxide. This new catalyst is both easy to prepare and stable for many hours. Operando X-ray absorption spectroscopic data reveal that the catalyst is made of nanoclusters of gamma-FeOOH covalently linked to the edge sites of a gamma-NiOOH support. According to density functional theory computations, this structure allows a reaction path involving iron as the oxygen evolving center and a nearby terrace O site on the gamma-NiOOH support oxide as a hydrogen acceptor. This bifunctional mechanism circumvents the aforementioned maximum activity limit associated with the scaling relationship and leads to superior OER activity.<br>