Selenium-modulated Pt/Al2O3 electronic structure induces deactivation during catalytic CO oxidation

Abstract

Industrial sources, such as steel and power activities continue to emit substantial amounts of CO, but have not received the same level of attention as mobile sources due to a lack of relevant regulations. This work reports that a commercial Pt/Al₂O₃ catalyst used in vehicle CO catalytic converters may face severe selenium (Se) poisoning deactivation from industrial sources. The turnover frequency (TOF) of the Pt/Al₂O₃ catalyst (250 °C) decreased from 2.18 s⁻¹ to 0.12 s⁻¹ with only 0.49 wt% (ICP) Se deposition. Se deposition causes the Pt 5d orbital shift to a higher energy state, raising the oxidation state of platinum. As a result, the back-donation from the 5d electrons of Pt to the 2π* antibonding orbital of the adsorbed CO molecule is inhibited, weakening the bonding between Pt/Al₂O₃ and the CO antibonding orbital, thereby significantly reducing CO activation ability. DRIFTS results, combined with apparent and microscopic kinetics, indicate that the surface of Se deposited Pt/Al₂O₃ catalyst remains O* available (500 K, θ_O* = 0.16), and the rate-controlling step changes from O₂ + 2* → 2O* to CO + * → CO*. The work suggests that the application of CO catalytic oxidation technology for industrial source should fully consider the toxic effect of Se, but is often neglected.