Low temperature reforming of methane with CO₂ over Pt/CeO₂, Ni/CeO₂ and Pt-Ni/CeO₂ catalysts prepared by a solution-combustion method

This study investigates the low temperature reforming of methane with CO₂ over mono-metallic (Pt/CeO₂ and Ni/CeO₂) and bi-metallic (Pt-Ni/CeO₂) solid solution catalysts prepared by using a one-pot solution-combustion method. Various analytical techniques were employed to analyze the synthesized catalysts in order to correlate their physicochemical properties to their catalytic activity. Solid solution formation was confirmed by the lattice parameter shifting and Rietveld refinement analysis. Solid-solution formation enhanced the defective oxygen species. The TPR and TPD_s studies showed that the synergy between Pt and Ni enhanced the active oxygen species and metal-support interaction of the Pt-Ni/CeO₂ catalyst, which are beneficial for the higher adsorption of CH₄ and CO₂. Pt-Ni/CeO₂ catalysts have a higher amount of O₂²⁻, O₂⁻ species and A_D/A_F2g ratio followed by the NC and PC catalysts, as confirmed by the O₂-TPD, XPS and RAMAN analysis. Pt-based catalysts start the DRM reaction at 350 °C, whereas Ni/CeO₂ activates at a temperature 100 °C higher than Pt-Ni/CeO₂ and Pt/CeO₂. At 675 °C, Pt-Ni/CeO₂ showed ∼86% conversion of CO₂ and CH₄ with 100% selectivity of synthesis gas with a H₂/CO ratio of ∼1, while Pt/CeO₂ and Ni/CeO₂ shows ∼46.2 and ∼59.8% conversion, respectively. DFT calculations showed that the Pt-Ni/CeO₂ catalyst required lower activation energy than the monometallic catalyst to activate CH₄ and CO₂. We believe that the synergy between Ni and Pt enhanced the structural and electronic properties of Pt-Ni/CeO₂, which is responsible for its excellent performance at low temperature.