Operando Insights into Coke-Resistant Ni/SiO2@CeO2 Core-Shell Catalysts for Ethanol Steam Reforming

Abstract The development of stable and coke-resistant catalysts remains a major challenge for ethanol steam reforming, where deactivation is accelerated by carbon deposition and metal sintering. In this work, we report the synthesis and detailed characterization of a core-shell Ni/SiO2@CeO2 catalyst and compare its performance with bare Ni/SiO2. Transmission electron microscopy and X-ray diffraction confirmed the formation of dispersed Ni nanoparticles supported on SiO2 with a uniform CeO2 shell, while catalytic tests revealed that although both catalysts achieved nearly complete ethanol conversion at 500 °C, Ni/SiO2 suffered rapid deactivation, whereas Ni/SiO2@CeO2 maintained higher hydrogen productivity and significantly slower activity loss. Operando XAS and operando Raman spectroscopy provided direct evidence that the ceria shell suppresses coke accumulation by facilitating the oxidation of carbonaceous intermediates and modulating the reduction kinetics of Ni species. Post-reaction analyses confirmed the retention of the core-shell architecture and the participation of Ce in redox transformations with a lower coke formation rate in the Ni/SiO2@CeO2 catalyst (5.4 mg·h−1·gcat−1) in comparison to the Ni/SiO2 (20 mg·h−1·gcat−1). Thus, this study demonstrates that integrating a CeO2 shell onto Ni/SiO2 is an effective strategy to improve stability, and mitigate coke formation, positioning Ni/SiO2@CeO2 as a promising catalyst for efficient hydrogen production from renewable ethanol.