Nanoporous Gold-Supported Ceria for the Water–Gas Shift Reaction: UHV Inspired Design for Applied Catalysis

Inspired by model studies under ultrahigh vacuum (UHV) conditions, inverse monolithic gold/ceria catalysts are prepared using thermal decomposition of a cerium nitrate precursor on a nanoporous gold (npAu) substrate. Cerium oxide deposits throughout the porous gold material (pores and ligaments 30–40 nm) are formed. npAu disks and coatings were prepared with loadings of about 3 to 10 atom % of ceria. The composite material was tested for the water–gas shift (WGS) reaction (H₂O + CO → H₂ + CO₂) in a continuous flow reactor at ambient pressure conditions. Formation of CO₂ was observed at temperatures as low as 135 °C with excellent stability and reproducibility up to temperatures of 535 °C. The considerably increased thermal stability of the material can be linked to the presence of metal oxide deposits on the nanosized gold ligaments. The loss of activity after about 15 h of catalytic conversion with heating to 535 °C was only about 10%. Photoemission spectroscopy indicates a defect (Ce³⁺) concentration of about 70% on the surface of the cerium oxide deposits, prior to and after WGS reaction. Raman spectroscopic characterization of the material revealed that the bulk of the oxide is reoxidized during reaction.