Operando HERFD XANES and Kβ XES study on Co based alloy nanoparticles for Oxygen Evolution Reaction (OER) probing dynamic spin state and ele

Enhancing alkaline water splitting efficiency is critical for the widespread adoption of anion exchange membrane (AEM) electrolyzers. The oxygen evolution reaction (OER) is the key limiting step, and gaining a deeper understanding of transition metal-based catalysts under operating conditions is essential for design of improved electrocatalysts for OER. Our previous operando L-edge X-ray absorption spectroscopy (XAS) study on cobalt nanoparticles has revealed reversible oxidation and low-spin species formation at 1.65 V vs. RHE. However, L-edge XAS alone is challenging to fully distinguish between oxidation state changes, spin state transitions, and coordination environment evolution. To address this gap, we propose an operando study using high-energy-resolution fluorescence-detected X-ray absorption near-edge structure (HERFD-XANES) and X-ray emission spectroscopy (XES). These techniques will provide critical insights into the dynamic electronic structure of Co alloy catalysts.