After switching back to H2/He, the back-transient phase starts, which is shown in fig. . We still see a formation of products several seconds to minutes after the switch, which corresponds to the stored carbon and oxygen during the build-up phase, as the CO in the gas phase approaches zero within the first minute after the switch. Additionally, CO decreases faster than the RTD, which corresponds to an increased consumption after the switch. At the same time, we see a repeated overshoot over the steady-state formation rate in CH4, coinciding with a maximum in the H2O molar flow rate. We conclude that when the adsorption sites, which are previously blocked by CO become available again, the reaction rate starts to increase drastically, consuming additional CO from the gas phase and forming mainly CH4 and H2O. For the C2 and C3+ components, the molar flow rates also progress above the values expected from the RTD, indicating the hydrogenation of surface intermediates, even after CO hast been flushed out of the reactor. Furthermore, these hydrocarbons exhibit a second and simultaneous maximum around 15 s after the initial overshoot of CH4, which we attribute to the hydrogenation of the less reactive Cβ accumulated in the build-up phase.