Work

Activation of NiFe Oxide-Based OER Catalysts: Iron Determines the Growth of the Catalytically Active Phase in NiO

Year: 2025

Type: article

Abstract: Mixed nickel iron hydr-/oxides are nowadays the best performing alkaline O2 evolution electrocatalysts. It has been assumed that the activity of these catalysts is determined by surface species but that a conditioning of the bulk is necessary to achieve optimal performances. Only recently, research delved into the surface properties and the composition near the solid-liquid interface of such catalysts. Using sputter depth-profiling XPS, we compared pure nickel oxides with mixed nickel iron oxides and found that electrochemical transformation to (oxy-)hydroxides in the mixed oxide systems is limited to just a few nanometers at the surface, unlike pure nickel oxides, which transform deeper into the bulk. This suggests that non-surface-sensitive techniques may overlook the true active phase in mixed nickel iron oxide catalysts. Our results indicate that bulk transformation may not be essential for catalytic activity. We propose a model in which iron limits nickel oxidation and promotes charge transfer directly to the oxygen evolution reaction.

Source: Journal of The Electrochemical Society

DOI: 10.1149/1945-7111/ae0a87

Authors: Christopher Gort, Jan P. Hofmann

Language: English

Topic: Electrocatalysts for Energy Conversion

Subfield: Renewable Energy, Sustainability and the Environment

Field: Energy

Domain: Physical Sciences

SDG: Affordable and clean energy

Open Access status: green

Funders: Deutsche Forschungsgemeinschaft, Bundesministerium für Bildung und Forschung, Helmholtz-Zentrum Berlin für Materialien und Energie

Awards: Verbundvorhaben H2Giga_QT1.1: PrometH2eus -- Projektverbund zur optimierten Materialentwicklung für die technische H2-Erzeugung durch verbesserte Sauerstoffelektroden, G39246350, G4034228952, Einfluss der KatalysatorTrägerWechselwirkung auf die Aktivität und Stabilität von WasserspaltungsKatalysatoren