Single step combustion synthesized Cu/Ce_0.8Zr_0.2O₂ for methanol steam reforming: structural insights from <italic>in situ</italic> XPS and HRTEM studies

Single step combustion synthesized Cu (5–15 at.-%)/Ce0.8Zr0.2O2 materials containing highly dispersed copper have been assessed for methanol steam reforming (MSR). The activity patterns suggest Cu (10 at.-%)/Ce0.80Zr0.20O2 as the most active formulation, converting ~51% methanol at 300 °C at a gas hourly space velocity of 40,000 h-1 (W/F = 0.09 s). The in situ XPS experiments carried over the most active sample show a sharp falloff of Cu-surface concentration from a considerably high value of 26% before to 7.4% after the in situ MSR tests and it is associated with the complete reduction of oxidized Cu-species (Cu2+) to metallic copper (Cu0). These findings point to the sintering of copper during MSR which is attributed to be responsible for the deactivation observed with time on stream. Interestingly, the MSR activity is shown to be regenerated nearly completely through an intermediate in situ oxidation step in the consecutive cycles of methanol reforming.