Where did they go? Evaluating the stability of exsolved Ni-Co-Fe metallic nanoparticles under CO2 electrolysis conditions – Insights by operando NAP-XPS

Solid Oxide Electrolysis Cells (SOEC) offer great potential for converting renewable
energy into fuels, leveraging cheaper and more abundant catalysts compared to Proton Exchange
Membrane (PEM) electrolyzers. However, the high working temperatures of SOECs (600-800 ºC)
pose challenges, particularly for the fuel electrode, typically composed of metals like nickel (Ni),
prone to sintering. Exsolution has emerged as a promising strategy to address this issue by
anchoring metal nanoparticles to perovskite oxide electrodes, preventing agglomeration. This
process involves the migration of metal cations within the perovskite lattice, nucleating as
nanoparticles on the oxide surface. By controlling reducing conditions, fine-tuning of nanoparticle
size is achievable. Moreover, adjusting perovskite composition enables the exsolution of ternary
alloys, such as Ni-Fe-Co, which has shown enhanced electrochemical performance for CO2
electrolysis. However, long-term operation reveals a decline in electrocatalytic activity, attributed to
a decrease in the exsolved nanoparticle population. To address this, an operando NAP-XPS
experimental campaign is proposed to assess the stability of ternary alloy exsolved nanoparticles.
Furthermore, the energy tunability of synchrotron radiation is ideal for investigating operando and nondestructively
potential surface segregations, and interactions with the CO2 atmosphere under
cathodic polarization. This investigation aims to elucidate degradation mechanisms and establish a
stability window for the ternary exsolved nanoparticles/double perovskite electrode system,
ultimately improving the durability of the next generation of fuel electrodes for SOECs