Support Effect and Stability of Inverse Fe1(OH)x/Pt Single-Site Interfacial Structured Catalysts for Preferential CO Oxidation in H2

Abstract

Preferential oxidation of CO in hydrogen (PROX) has been regarded as a promising method for removing a trace amount of CO to a parts-per-million (ppm) level to provide pure hydrogen fuel for polymer-electrolyte membrane fuel cells. Recently, we reported that SiO2-supported Pt nanoparticles with atomically dispersed Fe1(OH)x decoration exhibited exceptional CO removal in a very broad temperature window of −75–107 °C in the PROX reaction because of enriched interfaces and remarkably high reducibility of the iron species. Here, we further investigated the support effect on the catalytic performance of this inverse Fe1(OH)x/Pt single-site interfacial structure, as well as their stabilities under high-temperature redox atmospheres. We found that Fe1(OH)x/Pt on nonreducible supports such as SiO2 and Al2O3 is more favorable for efficient CO removal than those on reducible supports (e.g., Fe2O3 and TiO2) in the PROX reaction. The inferior performance of the latter case is attributed to the creation of additional active interfaces to initiate competing H2 oxidation. High-temperature redox pretreatments of the optimized SiO2-supported Fe1(OH)x/Pt catalyst up to 500 °C did not cause any noticeable changes of the temperature window of complete CO removal, indicating that the inverse Fe1(OH)x/Pt single-site interface structure has high thermal stability against sintering. Further increasing the H2 concentration did not change the temperature window either. The above results suggest that the inverse Fe1(OH)x/Pt catalyst is very robust with high potential for practical applications and other catalytic reactions.