Shining a light on methane dry reforming - exploring the impact of visible light on carbon formation over Co/xCeO2-Al2O3

Introducing light to thermal DRM may be an effective strategy to improve catalyst stability, but light's role in the stability mechanism is not well understood. This study systematically moderated the support's basicity and oxygen release capacity by synthesising several cobalt-impregnated (10 wt% Co) xCeO(2)-Al2O3 supports (xCe-Al, x = 0, 5, 10 and 20 mol%) to investigate light's impact on carbon formation and the CH(x )oxidation and dehydrogenation rates (x = 0-3). The support's reducibility and CO2 uptake increased with Ce content, arising from oxygen vacancies created upon surface reduction. Co/Al was the most active (29% CO2 and 18% CH4 conversion at 650 degrees C), and the activity and selectivity (H-2/CO) decreased with Ce concentration due to ceria's propensity for RWGS and/or the Co size increase upon Ce incorporation (after reduction, from 13 nm for Co/Al to 36 nm for Co/20Ce-Al). Co/Al deactivated the most by carbon accumulation (4.6 wt%, 7 h stability test, 650 degrees C), as the support provided no O for CHx oxidation (x = 0-3). Introducing Ce improved the carbon content and stability under thermal conditions due to ceria's oxygen release capacity from oxygen vacancies (0.78 wt% for Co/5Ce-Al). Visible light (2.0 W cm-2) improved CH4 conversion of Co/xCe-Al, but the increased CHx dehydrogenation rate accelerated carbon deposition for all catalysts, harming the stability. In situ DRIFTS identified no CHxO intermediate, suggesting poor CHx oxidation rates relative to CHx dehydrogenation. These findings highlight that sufficient support oxygen release is necessary to facilitate CHx oxidation, achieving light-facilitated stability improvements.