Issue 8, 2023

Demonstrating the source of inherent instability in NiFe LDH-based OER electrocatalysts

Abstract

Nickel-iron layered double hydroxides are known to be one of the most highly active catalysts for the oxygen evolution reaction in alkaline conditions. The high electrocatalytic activity of the material however cannot be sustained within the active voltage window on timescales consistent with commercial requirements. The goal of this work is to identify and prove the source of inherent catalyst instability by tracking changes in the material during OER activity. By combining in situ and ex situ Raman analyses we elucidate long-term effects on the catalyst performance from a changing crystallographic phase. In particular, we attribute electrochemically stimulated compositional degradation at active sites as the principal cause of the sharp loss of activity from NiFe LDHs shortly after the alkaline cell is turned on. EDX, XPS, and EELS analyses performed after OER also reveal noticeable leaching of Fe metals compared to Ni, principally from highly active edge sites. In addition, post-cycle analysis identified a ferrihydrite by-product formed from the leached Fe. Density functional theory calculations shed light on the thermodynamic driving force for the leaching of Fe metals and propose a dissolution pathway which involves [FeO4]2− removal at relevant OER potentials.

Graphical abstract: Demonstrating the source of inherent instability in NiFe LDH-based OER electrocatalysts

Supplementary files

Article information

Article type
Paper
Submitted
15 Sept. 2022
Accepted
16 Janv. 2023
First published
17 Janv. 2023
This article is Open Access
Creative Commons BY license

J. Mater. Chem. A, 2023,11, 4067-4077

Demonstrating the source of inherent instability in NiFe LDH-based OER electrocatalysts

D. Tyndall, M. J. Craig, L. Gannon, C. McGuinness, N. McEvoy, A. Roy, M. García-Melchor, M. P. Browne and V. Nicolosi, J. Mater. Chem. A, 2023, 11, 4067 DOI: 10.1039/D2TA07261K

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