Determining the Surface Atomic Population of CuₓNi₁–ₓ/CeO₂ (0 < x ≤ 1) Nanoparticles during the Reverse Water–Gas Shift (RWGS) Reaction

The comprehension of surface atomic phenomena of nanoparticles is indispensable for the improvement of future catalysts. In this work, CuₓNi₁–ₓ/CeO₂ (0 < x ≤ 1) nanoparticles were synthesized and used in the RWGS reaction. The influence of the nanoparticle composition, surface atomic population, and strong metal–support interaction (SMSI) effect on the reactivity toward CO₂ dissociation was investigated by probing the electronic and structural properties of the nanoparticles using the state-of-the-art techniques, such as near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS), in situ time-resolved X-ray absorption near-edge spectroscopy (XANES), and in situ extended X-ray absorption fine structure (EXAFS). An investigation into the nanoparticle surface revealed that its composition has a direct impact on the nanoparticles’ reactivity. The Ni atoms migrate toward the surface of the nanoparticles during the RWGS reaction. The nanoparticles showing the SMSI effect (Cu-richer ones) present Ni-richer surfaces, and it has a negative influence on their reactivity toward CO₂ dissociation. The SMSI effect is responsible for blocking the catalytic active sites on the nanoparticle surface by the capping layer from the support that surrounds the nanoparticle surface and then worsening the reactivity toward CO₂ dissociation.