Investigating the phase-dependent OER behaviour of Ni (oxy)hydroxide

The oxygen evolution reaction (OER) is a critical step in electrochemical water splitting, yet its sluggish kinetics hinder efficiency. Nickel (oxy)hydroxides have emerged as promising electrocatalysts, but the role of different Ni phases, particularly γ-NiOOH, in enhancing OER performance remains unclear. This study aims to investigate phase-dependent OER behavior by utilizing in-situ Ni L-edge X-ray absorption spectroscopy (XAS) at the BL24 beamline of ALBA. Compared to conventional Ni K-edge XAS, Ni L-edge soft XAS provides surface-sensitive insights, particularly when using electron yield (EY) detection to minimize bulk contributions. We will employ 3 nm Ni nanoparticles synthesized via gas aggregation to avoid ligand contamination and ensure a well-defined passivation layer. By controlling cyclic voltammetry (CV) conditioning rates, we will induce distinct phase transitions—fast conditioning (100 mV/s) favoring α-Ni(OH)₂ ↔ γ-NiOOH and slow conditioning (1 mV/s) promoting β-Ni(OH)₂ ↔ β-NiOOH—to compare their OER activity. The results will clarify the role of γ-NiOOH in OER, advance mechanistic understanding, and contribute to the design of improved Ni-based electrocatalysts. This study also aims to expand the application of in-situ soft XAS for probing electrocatalytic interfaces under operating conditions.