Methane oxidation with low Pt2+ catalyst: High activity and stability against SO2, NO, and H2O poisoning

• Low-loaded Pt 2+ catalysts were prepared using a simple incipient impregnation method. • The catalyst shows high Pt dispersion and high activity for methane oxidation at low temperatures. • The catalyst resists deactivation in lean exhaust conditions containing SO 2 , NO, and H 2 O. • Surface Pt 4+ species and Pt 2+ /ZrO 2 interface enhance the adsorption of oxygen and methane molecules. • Stability of the catalyst is explained using energy-level alignment at the Pt/ZrO 2 interface. We report the exceptional performance of a Pt/ZrO 2 catalyst with highly dispersed 3.5 at % Pt loading for methane oxidation, demonstrating its outstanding resistance to deactivation in lean exhaust conditions, which contain SO 2 , NO, and H 2 O. X-ray photoelectron spectroscopy analysis of fresh and used catalysts revealed the presence of Pt 2+ and Pt 4+ surface species, even under these challenging reaction conditions. A mechanism is proposed to highlight the synergistic roles of Pt 4+ species for oxygen adsorption and the Pt 2+ /ZrO 2 interface for methane adsorption, reducing the competition between the reacting molecules. Despite an increase in apparent activation energy in the presence of SO 2 , NO, or H 2 O, the catalyst retains its high activity. The high methane oxidation activity of the catalyst is attributed to the higher velocity of methane molecules, resulting in more frequent and successful collisions at Pt 2+ /ZrO 2 interface compared to other species in engine exhaust. The enhanced stability of the Pt 2+ surface species is further explained by the energy-level alignment at the Pt 2+ /ZrO 2 interface, which is driven by the interfacial work function values of Pt 2+ surface species and n-type semiconductor ZrO 2 . The results highlight the potential of Pt/ZrO 2 catalyst for efficient and stable methane oxidation in real-world exhaust environments of natural gas engines.