XAS/DRIFTS/MS spectroscopy for time-resolved operando study of integrated carbon capture and utilisation process

An integrated carbon capture and utilization (ICCU) process present an ideal solution to address anthropogenic carbon dioxide (CO ₂) emissions from fossil fuel-driven electricity production, allowing for capturing and subsequent utilization of CO ₂ instead of current release into the atmosphere. Effective dual-functional materials (DFMs), through the combination of CO ₂ sorbents and catalysts, can not only capture CO ₂ but also convert it into higher-value chemicals, such as CH ₄ or CO, under isothermal conditions within a single reactor are highly desirable for ICCU processes. In this study, we investigate the mechanism of ICCU over 10 %NiCaO by the time-resolved operando XAS/DRIFTS/MS and the influence of a reduction pretreatment on the process and the products formed. During the 1st stage of the ICCU process (carbon capture), CaO adsorbs CO ₂ resulting in bicarbonate, carbonate, and formate species formation. At the same time, the Ni catalytic active species are oxidized by CO ₂, leading to the formation of NiO and CO. However, pre-treating the same DFM under hydrogen, during heating to operating temperature, resulted in a switch to CH ₄ production, suggesting the presence of high levels of surface adsorbed H ₂. During the 2nd stage of ICCU (CO ₂ conversion), the NiO generated during capture is reduced by H ₂ to metallic Ni, which facilitates the reduction of bicarbonates, carbonates, and formats, via H ₂ dissociation, to produce and liberate gaseous CO. Thus, both adsorption and catalytic sites are regenerated for the subsequent ICCU cycle.