Competitive Interactions between Propylene Combustion Products Regulate Catalyst Durability over Facet-Tuned Pt/TiO2

Abstract

While product-induced inhibition is widely recognized in heterogeneous catalysis, the joint influence of co-generated products on time-dependent catalytic deactivation remains underexplored. Herein, uniform colloidal Pt nanoparticles were deposited on anatase TiO2 supports selectively exposing (101) or (001) facets to fabricate two facet-controlled model Pt/TiO2 catalysts. We uncovered the intrinsic deactivation mechanism for low-temperature lean propylene combustion via stability tests, alternating feed kinetics, in situ DRIFTS, and density functional theory (DFT) calculations. Time-on-stream reaction tests recorded persistent activity decay for both catalysts, with far more serious decay observed on Pt/TiO2(101). Multiple characterization results excluded Pt sintering/encapsulation, C3H6/O2 poisoning, and partial Pt oxidation as dominant degradation factors. Instead, CO2 adsorption and subsequent carbonate accumulation on TiO2 surfaces were identified as the primary deactivation sources, which cut off supplementary oxygen delivery at metal–support interfaces. DFT adsorption energy data proved that H2O possessed a stronger surface affinity than CO2 on both facet types, and in situ generated H2O competed for adsorption sites to curb carbonate accumulation. Apart from this competitive effect, reaction-derived H2O alleviated excessive coverage of Pt sites by C3H6 and facilitated the adsorption and activation of gas-phase O2. Thanks to the relatively high water-binding capacity of TiO2(001), the corresponding Pt/TiO2(001) catalyst maintained abundant interfacial water during operation and exhibited much milder carbonate-triggered decay. These findings clarified the competitive co-adsorption interplay between CO2 and H2O across Pt–TiO2 interfaces and offered general kinetic guidance for developing durable catalysts toward industrial hydrocarbon lean combustion.