Reactive Capture and Conversion of CO 2 into Hydrogen over Bifunctional Structured Ce 1- x Co x NiO 3 /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 CO 2 to marketable chemicals and fuels appears to be a sustainable approach to not only curb greenhouse emissions but also transform wastes like CO 2 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 CO 2 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- x Co x NiO 3 perovskite-type oxide catalysts for the dual-purpose use of capturing CO 2 and reforming CH 4 for H 2 production. Three honeycomb monoliths composed of equal amounts of adsorbent and catalyst constituents with varied Ce 1- x Co 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), N 2 physisorption, X-ray photoelectron spectroscopy (XPS), H 2 -TPR, in situ CO 2 adsorption/desorption XRD, and NH 3 -TPD. Results showed that the Ce 1- x Co 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, CO 2 adsorption/desorption reversibility, and oxygen species availability. Assessing the structured BFM monoliths via combined CO 2 capture and CH 4 reforming in the temperature range 500-700 °C revealed that such differences in physiochemical properties lowered H 2 and CO yields at higher cobalt loading, leading to best catalytic performance in Ce 0.75 Co 0.25 NiO 3 /Ca sample that achieved 77% CO 2 conversion, 94% CH 4 conversion, 61% H 2 yield, and 2.30 H 2 /CO ratio at 700 °C. The stability of this BFM was assessed across five adsorption/reaction cycles, showing only marginal losses in the H 2 /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 CO 2 capture and utilization in H 2 production processes.