Highly stable core-shell Pt-CeO2 nanoparticles electrochemically deposited onto Fecralloy foam reactors for the catalytic oxidation of CO

Core-shell catalysts, consisting of active (noble) metal nano-particles surrounded by porous oxides, have drawn much attention because of their enhanced activity and (thermal) stability in several catalytic processes such as the oxidation of CO and hydrocarbons, the water-gas shift, the CO2 reforming of methane, as well as in photocatalysis and electrocatalysis. Interactions of metal particles with oxide supports can radically enhance the performance of supported catalysts: high catalytic activity is normally ascribed to the formation of particularly active sites at the noble metal-metal oxide interface, whose surface area may become very large when nanometric metal cores are encapsulated by porous oxide shells. In this work, we have investigated a totally electrochemical method consisting of two sequential cathodic deposition steps to prepare of low Pt-loading structured catalysts based on reticulated Fecralloy open foams, that are ideal supports to realize catalytic reactors suited for many industrially relevant energy and environmental applications. In particular, this preparation strategy allows the facile deposition of a protective and promoting CeO2 shell over in-situ pre-formed Pt nanoparticles directly anchored onto the 3D shaped metallic foam substrates. The catalytic oxidation of CO was selected to investigate the effects induced by the core-shell architecture of CeO2-Pt nano-particles on the intrinsic activity in the temperature range 200 - 300 °C and on the thermal stability under oxidizing conditions up to 800 °C. The CO oxidation mechanism was insensitive to the addition of CeO2 overlayer on Pt particles, as confirmed by the unchanged apparent activation energy and reaction order with respect to both CO and O2. Nevertheless, the specific reaction rate per gram of Pt increased significantly, due to the formation of novel active sites at the CeO2-Pt interface, which are less prone to be "poisoned" by strongly adsorbed CO molecules. Moreover, the application of a CeO2 overlayer onto Pt nanoparticles induced a remarkable stabilization effect against sintering and extensive reconstruction of the active phase up to 800 °C