Operando study on wet CO oxidation over ceria and alumina supported platinum catalysts

Journal article, 2026

The effect of water on carbon monoxide oxidation activity of highly dispersed Pt/ceria and Pt/alumina catalysts with narrow Pt particle size distributions at around 1–2 nm has been studied by kinetic measurements and infrared spectroscopic characterisation under in situ and operando conditions. Water promotes the low-temperature activity for both catalysts, however, by different mechanisms. For Pt/ceria, the reaction proceeds with a very weak dependence on water concentration whereas the apparent activation energy increases. It is proposed that water, on the one hand, promotes the Mars-van Krevelen mechanism through destabilisation of ceria lattice oxygen favouring its reaction with CO and/or desorption of product CO2 and, on the other hand, turn ionic Pt clusters active for CO oxidation. For Pt/alumina, the CO oxidation proceeds via Langmuir–Hinshelwood mechanism on Pt, however, with a positive dependency on water concentration. Likely water both weakens the interaction between CO and Pt, and may enable the proposed reaction pathway between CO and OH ad-species to form surface carboxylates as part of a wet CO oxidation mechanism.