CO₂ hydrogenation to methane over Ni/ZrO₂ and Ni/CeO₂ catalysts: experimental and DFT studies

In this paper, performance of ZrO₂ and CeO₂ supported Ni catalysts on CO₂ hydrogenation reaction was investigated in continuous flow reactor. The results revealed that Ni/ZrO₂ catalyst exhibited superior performance compared to Ni/CeO₂, with a CO₂ conversion rate of 71.84%, a CH₄ formation rate of 21.03 mmol g⁻¹ h⁻¹, and excellent reaction stability at 400 °C. And the activation energy of Ni/ZrO₂ was lower than that of Ni/CeO₂. N₂ adsorption–desorption, SEM, XRD, XPS, CO₂-TPD and O₂-TPO analysis results suggest that Ni/ZrO₂ is a multi-stage pore material, which has slit holes formed by the accumulation of sheet-like particles, as well as a superior dispersion of Ni on ZrO₂. Moreover, Ni/ZrO₂ shows higher alkalinity and remarkable resistance to carbon accumulation. DFT calculations demonstrated that CO₂ can be more easily adsorbed on ZrO₂ surface, and one O-terminus of CO₂ is closer to top sites of ZrO₂, which is favorable for electron transfer and promotes the activation of CO₂.