Flame Synthesized Co–CeO<sub>2</sub> Catalysts for CO<sub>2</sub> Methanation
Angelina Evtushkova, Jason M. J. J. Heinrichs, Alexander Parastaev, Nikolay Kosinov, Emiel J. M. Hensen
Abstract
High Resolution Image Download MS PowerPoint Slide Achieving selective conversion of CO 2 to CO, CH 4, or CH 3 OH remains a key challenge in catalyst design for CO 2 hydrogenation. Site-specific activity at the metal–support interface plays a crucial role, motivating efforts to optimize metal particles and their interactions with supports. In this study, we synthesized Co-CeO 2 catalysts with varying Co contents via flame spray pyrolysis (FSP) to investigate how the location and structure of Co influence activity. All samples contain ∼8 nm CeO 2 nanoparticles with a high surface area and approximately 3.8 mol % Co 2+ ions strongly interacting with CeO 2 . Catalysts with ≥5 mol % Co feature segregated CoO and Co 3 O 4 particles, which are partially reduced to metallic Co at 300 °C. The highest Co-weight-normalized activity at 200 °C (3.9 ± 0.2 mmol CO 2 /mol Co/s, CH 4 selectivity 85%) was observed in 10 mol % Co-CeO 2, with ∼50% Co reduction and 4–5 nm Co nanoparticles. The 2.5 mol % Co sample exhibited only 10% reduction, forming small Co clusters and creating Co 2+ –O–Ce sites that mainly favor CO formation (79% selectivity). Low Co content facilitates CO 2 hydrogenation to CO and minor CH 3 OH formation, likely on oxygen vacancies, assisted by H 2 dissociation on very small metallic Co clusters. Larger Co nanoparticles predominantly produce CH 4, with minor CO and no CH 3 OH. These results demonstrate that FSP enables tuning of catalyst structures for selective CO 2 hydrogenation, leveraging the synergy between small metallic Co particles and Co 2+ –O–Ce sites.