For the multipulse experiments we first oxidized the Ru/Al2O3 catalyst in an O2/N2 gas mixture (1:1, 150 °C, 30 min, O150) and reduced it subsequently by exposing it to a sequence of CO/Ar pulses at 190 °C (for details see ref. ). Subsequently, we determined the dynamic activity for CO2 methanation by exposing the catalyst to a sequence of CO2/H2/Ar (4:1:1) pulses at 190 °C. Typically, we adjusted the number of pulses such that in the end of the sequence there was no significant change in the signal of the consumed species any more, indicating that the catalyst had reached steady-state conditions. The separation time between pulses (t) was adjusted such that the next pulse started after the Ar signal of the preceding pulse had decayed to the background signal (≈ 0.4% of the pulse maximum), where the background is defined by the intensity before and after the pulse sequence. Note that for the other gases the background level may not necessarily be reached, which can result in an increase of the measured minimum intensity between the pulses. For these reactants and products, which interact more strongly with the catalyst, the resulting signal intensities can contain a contribution from the preceding pulse, resulting from the longer tailing of the pulse than the pulse separation. However, this is largely compensated by a similar contribution of this pulse to the following one.