Synergistic performance of Ni-Ca based dual functional materials under the coexistence of moisture and oxygen in CO2 source for integrated carbon capture and utilisation

Abstract

Global warming and climate change require urgent reduction of CO2 emissions. Integrated carbon capture and utilisation combined with dry reforming of methane (ICCU-DRM) has the potential to mitigate greenhouse gas emissions by capturing and converting CO2 and CH4 into valuable syngas. However, the performance and stability of dual-functional materials (DFMs) are unclear under real-world flue gas conditions, particularly in the presence of steam and O2. In this study, we elucidated the mechanisms of the performance of a Ni0.05/CaO0.95 DFM under various flue gas conditions and investigated the combined effects of steam and O2 on CO2 uptake, CO and H2 yields and cyclic stability. Our approach includes the synthesis and evaluation of the DFM using advanced characterisation techniques, such as XRD, in-situ infrared spectroscopy, CH4-TPR, SEM, EXD, FIB-SEM, BET, and XPS, to gain insights into the properties and behaviour of the DFM under different flue gas conditions. The findings show that under the simulated flue gas condition (10.0 % CO2 + 6.0 % H2O + 6.7 % O2/N2), there was a significant deterioration in performance, with CO2 uptake of only 5.7 mmol.g-1, average H2 yield of 11 mmol.g−1 and average CO yield of 6.2 mmol.g−1. While under the ideal condition (10.0 % CO2/N2), the CO2 uptake, average H2 yield and average CO yield were 10.7 mmol.g−1, 16.9 mmol.g−1 and 23.1 mmol.g−1, respectively. FIB-SEM and XPS analysis highlighted the combined effect of steam and O2 on the performance of Ni0.05/CaO0.95 DFM during ICCU-DRM. Notably, the presence of O2 promoted the oxidation of Ni, resulting in decreased catalytic activity and volumetric expansion of Ni particles. Furthermore, the presence of steam promoted CO2 adsorption, inducing additional volumetric expansion of the CaO component of DFM. These synergistic expansions form a dense shell on the surface, hindering the reduction of internal NiO, thereby diminishing DFM performance.