Host, Suppressor, and Promoter—The Roles of Ni and Fe on Oxygen Evolution Reaction Activity and Stability of NiFe Alloy Thin Films in Alkaline Media

By Fuxi Bao, Erno Kemppainen, I. Dorbandt, Fanxing Xi, Radu Bors, N. Maticiuc, R. Wenisch, Rory Bagacki, Christian Schary, Ursula Michalczik and 5 more. ACS Catalysis, 2021

182 citations recorded by the source corpus.

Understanding the oxygen evolution reaction (OER) activity and stability of the NiFe-based materials is important for achieving low-cost and highly efficient electrocatalysts for practical water splitting. Here, we report the roles of Ni and Fe on the OER activity and stability of metallic NiFe and pure Ni thin films in alkaline electrolyte. Our results support that the Ni(OH) 2 /NiOOH does not contribute to the OER directly, but it serves as an ideal host for Fe incorporation, which is essential for obtaining high OER activity. Furthermore, the availability of Fe in the electrolyte is found to be important and necessary for both NiFe and pure Ni thin films to maintain enhanced OER performance, while the presence of Ni is detrimental to the OER kinetics. The impacts of Fe and Ni species present in KOH on the OER activity are consistent with the dissolution/re-deposition mechanism we propose. Stability studies show that as long as Fe (both co-electrodeposited Fe and incorporated Fe) is present in the electrocatalyst film, the OER activity will degrade under prolonged continuous operation. Satisfactory stability can, however, be achieved with intermittent OER operation in which the catalyst cycles between a degraded and recovered state. Accordingly, two important ranges, i.e., the recovery range and the degradation range, are proposed. Prolonged continuous OER operation (i.e. in the degradation range) generates NiOOH in the electrocatalyst which likely enhances the formation of FeOOH and eventually leads to the OER deactivation. If the electrode works in the recovery range for a certain period, i.e., at a sufficiently low reduction potential, where the Ni 3+ is reduced to Ni 2+ , the OER activity can be maintained (and even improved).

Subfields: Electrical and Electronic Engineering, Electrochemistry, Renewable Energy, Sustainability and the Environment

View Paper: https://www.semanticscholar.org/paper/dade8ad3a73d106730d99cd058f2943a20e79a8a