Reactive Capture and Conversion of CO2 into Hydrogen over Bifunctional Structured Ce1–xCoxNiO3/Ca Perovskite-Type Oxide Monoliths

Carbon capture, utilization, and storage (CCUS) technologies are pivotal for transitioning to a net-zero economy by 2050. In particular, conversion of captured CO₂ to marketable chemicals and fuels appears to be a sustainable approach to not only curb greenhouse emissions but also transform wastes like CO₂ into useful products through storage of renewable energy in chemical bonds. Bifunctional materials (BFMs) composed of adsorbents and catalysts have shown promise in reactive capture and conversion of CO₂ at high temperatures. In this study, we extend the application of 3D printing technology to formulate a novel set of BFMs composed of CaO and Ce_1-xCo_xNiO₃ perovskite-type oxide catalysts for the dual-purpose use of capturing CO₂ and reforming CH₄ for H₂ production. Three honeycomb monoliths composed of equal amounts of adsorbent and catalyst constituents with varied Ce_1-xCo_x ratios were 3D printed to assess the role of cobalt on catalytic properties and overall performance. The samples were vigorously characterized using X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), N₂ physisorption, X-ray photoelectron spectroscopy (XPS), H₂-TPR, in situ CO₂ adsorption/desorption XRD, and NH₃-TPD. Results showed that the Ce_1-xCo_x ratios-x = 0.25, 0.50, and 0.75-did not affect crystallinity, texture, or metal dispersion. However, a higher cobalt content reduced reducibility, CO₂ adsorption/desorption reversibility, and oxygen species availability. Assessing the structured BFM monoliths via combined CO₂ capture and CH₄ reforming in the temperature range 500-700 °C revealed that such differences in physiochemical properties lowered H₂ and CO yields at higher cobalt loading, leading to best catalytic performance in Ce_0.75Co_0.25NiO₃/Ca sample that achieved 77% CO₂ conversion, 94% CH₄ conversion, 61% H₂ yield, and 2.30 H₂/CO ratio at 700 °C. The stability of this BFM was assessed across five adsorption/reaction cycles, showing only marginal losses in the H₂/CO yield. Thus, these findings successfully expand the use of 3D printing to unexplored perovskite-based BFMs and demonstrate an important proof-of-concept for their use in combined CO₂ capture and utilization in H₂ production processes.