Novel Insights on the Metal-Support Interactions of Pd/ZrO₂ Catalysts on CH₄ Oxidation

With the environmental harm of unburnt CH₄ in natural gas vehicle exhaust, oxidizing CH₄ to CO₂ over catalysts at low temperatures becomes an exigent issue. Supported Pd catalysts possess higher CH₄ activity than other noble metal catalysts. A series of Pd/ZrO₂ catalysts were synthesized to research the potential relationship among Pd particle morphology, electron transfer, CH₄ oxidation mechanism, and catalytic activity. Characterizations show that the ratio of PdO facets to edge/corner sites on four catalysts increases in the order of PZ85 ≈ PZ40 < PZ55 < PZ70 because of the difference in content of surface -OH groups, and this order turns out to be the same as that of electron transfer intensity, revealing the degree of metal-support interactions. This kind of metal-support interaction in PZ70 can be helpful to accelerate CH₄ combustion via promoting the break of the C-H bond and dissociation of CO₃* according to density functional theory studies. T₉₀ of the PZ70 catalyst with optimum catalytic activity reaches 331 °C.