Toward More Cost-Effective Hydrogen Production: Magnetron-Sputtered Ni- and Co-Based CeO₂ Catalysts at Ultralow Metal Loading

A series of mono- and bimetallic Ni- and Co-based catalysts supported on nanocrystalline cerium oxide (CeO₂) was prepared by magnetron sputtering with a total metal loading of only 0.2 wt % to investigate the influence of the deposition sequence on the ethanol steam reforming (ESR) reaction. Structural analyses by X-ray Diffraction (XRD) and Scanning Transmission Electron Microscopy-Energy-Dispersive X-ray Spectroscopy (STEM-EDS) confirmed that the sputtering process produced highly dispersed metallic species without detectable crystalline domains, while maintaining the mesoporous structure of the CeO₂ support. Among the catalysts, Ni-Co/CeO₂, obtained by sequential deposition of Co followed by Ni, exhibited the lowest deactivation rate constant (kd = 9.93 × 10^-3 h^-1), highest stability, and H₂ selectivity sustained over 28 h of reaction. Postreaction characterization by EDS mapping, Thermogravimetric Analysis-Derivative Thermogravimetry (TGA-DTG), and Raman spectroscopy revealed minimal coke deposition on Ni-Co/CeO₂, whereas the Co-Ni and NiCo counterparts suffered from higher carbon accumulation and faster deactivation. These results demonstrate that the metal deposition order critically governs the catalytic performance and that magnetron sputtering enables precise surface control even at ultralow metal loadings, producing catalysts with remarkable activity, stability, and coke resistance. Thus, herein, we highlight that magnetron sputtering is a promising route for designing efficient and economically viable reforming catalysts, which opens perspectives for exploring electronic and interfacial effects at higher metal loadings.