Partial oxidation of methane over high coke-resistant bimetallic Pt-Ni/CeO₂ catalyst: Profound influence of Pt addition on stability

We have developed a bimetallic Pt-Ni/CeO₂ catalyst by straightforward citric acid complex combustion method for low-temperature partial oxidation of methane. Furthermore, we also compared the catalytic performance of bimetallic Pt-Ni/CeO₂ with monometallic Ni/CeO₂ catalysts. The bimetallic 0.5%Pt-2.5%Ni/CeO₂ (PNC2.5) catalyst exhibited >99% conversion of methane with a H₂/CO ratio of 2, whereas monometallic 2.5%Ni/CeO₂ (NC2.5) catalyst showed ∼92% methane conversion with a H₂/CO ratio of 1.9 at 700 °C. In addition, the PNC2.5 catalyst does not show any deactivation and structural changes during 500 h time-on-stream (TOS), also confirmed by TEM, Raman, and TGA analysis. Conversely, a substantial activity loss (∼61%) was noticed in the NC2.5 catalyst owing to the coking and sintering of Ni species. The excellent performance of the PNC2.5 catalyst can be attributed to the modified electronic-structural properties. The activation of CH₄ molecules was studied by DFT calculation over Pt-Ni/CeO₂(111) and Ni/CeO₂(111) model systems, which explain the promotional effect of Pt in the methane C-H bond activation with ∼8 kcal/mol reduction in the activation barrier.