Enhanced Reducibility of the Ceria-Tin Oxide Solid Solution Modifies the CO Oxidation Mechanism at the Platinum-Oxide Interface

Many important catalytic reactions take place at metal-oxide interfaces. However, their mechanisms are typically difficult to probe due to the low concentration of active sites and the lack of highly sensitive spectroscopic methods. In this work, we analyze the impact of oxide reducibility on the mechanism of low-temperature CO oxidation over platinum nanoparticles supported on ceriabased solid solutions. We demonstrate that the easier reducibility of Ce4+ at the Pt/ Ce0.5Sn0.5O2 interface (in comparison to that for Pt/CeO2) increases the catalytic CO oxidation rate, lowers the apparent activation energy, and increases the reaction order in oxygen. Operando time-resolved X-ray absorption spectroscopy suggests that the Ce4+ reduction rate at the Pt/Ce0.5Sn0.5O2 interface is accelerated, while the Ce3+ oxidation rate becomes rate-limiting. Importantly, no reduction of Sn4+ in the ceria-tin solid solution and no formation of Pt/Sn alloys were detected under relevant reaction conditions using in situ X-ray absorption spectroscopy, ambient-pressure X-ray photoelectron spectroscopy, and infrared spectroscopy. This work provides a better understanding on the reactivity of interfaces. It demonstrates that the reducibility of the oxide close to a metal strongly influences catalytic rates, which provides ideas for the design of better catalysts.

Automated summary

This study examines the impact of oxide reducibility on the mechanism of low-temperature CO oxidation over platinum nanoparticles supported on ceriabased solid solutions. It demonstrates that the reducibility of the oxide near a metal influences catalytic rates, providing insights for the design of better catalysts. The study utilizes operando time-resolved X-ray absorption spectroscopy to reveal accelerated Ce4+ reduction rate at the Pt/Ce0.5Sn0.5O2 interface.