Methanation of CO2: Structural response of a Ni-based catalyst under fluctuating reaction conditions unraveled by operando spectroscopy

•Maximum CO2 conversion of 81% at 400 °C obtaining 80% CH4.•Operando XAS study during methanation of CO2 under changing reaction conditions.•Significant changes in the structure of the Ni particles under reaction conditions.•Deactivation of the catalyst in the second methanation cycle after H2 dropout.•Partial oxidation of Ni particles leads to lower catalytic methanation performance.

The methanation of CO2 as a relevant strategy for energy storage has been studied by operando X-ray absorption spectroscopy under dynamic H2/CO2 and CO2 reaction atmospheres. A typical CO2 conversion of 81% was reached at 400 °C with a 23 wt.-% Ni/CaO–Al2O3 catalyst, yielding 80% of CH4. The operando XAS experiment under working conditions revealed pronounced structural changes, e.g., a fast bulk oxidation of the Ni particles after removal of H2 from the H2/CO2 (4:1) gas stream. A lower performance of the catalyst was observed in the subsequent methanation cycle due to the presence of a residual oxidized fraction of Ni.

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