[Zurück]

F. Mirabella, M. Müllner, T. Touzalin, M. Schmid, M. Koper, G. Parkinson, U. Diebold:
"Ni modified Fe₃O₄(001) surface as a simple model system for understanding the Oxygen Evolution Reaction";
Vortrag: DPG-Frühjahrstagung (DPG Spring Meeting) of the Surface Science Division, SurfaceScience21, virtual; 01.03.2021.

Electrochemical water splitting is an environmentally friendly technology to store renewable energy in the form of chemical fuels. Among the Earth-abundant first-row transition metal-based catalysts, mixed Ni-Fe oxides have shown promising performance for effective and low-cost catalysis of the oxygen evolution reaction (OER) in alkaline media, but the synergistic roles of Fe and Ni cations in the OER mechanism remain unclear. In this work, we report how the Ni-modification changes the reactivity of a model iron oxide catalyst using a combination of surface science techniques in ultra-high-vacuum (LEED, XPS, LEIS, STM), AFM in air, and electrochemical methods (CV and EIS) in alkaline media. A significant improvement in the OER activity is observed when the surface presents an Fe:Ni ratio in the range 20-40%, which is in good agreement with what has been observed for powder catalysts. EIS suggests that the OER precursor species observed on the clean and Ni-modified surfaces are similar, but form at lower overpotentials when the surface Fe:Ni ratio is optimized. We propose that the well-defined Fe3O4(001) surface can serve as a model system for understanding the OER mechanism on mixed Fe/Ni oxides.