The mixture of K-Li4SiO4 mixed with Ni/Al2O3 was used as the dual functional materials for ICCU-DRM (https://doi.org/10.1016/j.seppur.2021.119476). Some researchers might argue that the physical mixture should not be called dual functional materials, instead, could be named as combined materials. After 10 cycles of ICCU-DRM, the migration of Ni species was observed, corresponding to the sintering of Ni particles. The reaction between sorbent and catalyst also resulted in the formation of LiAlO2. The following content is copied from the above reference.
“SEM images of K-Li4SiO4 and Ni/Al2O3 after 10 cycles are revealed in Fig. 6(a, b). It is found that the morphology of K-Li4SiO4 and Ni/Al2O3 remains unchanged after 10 ICCU-DRM cycles. However, some Ni is detected distributing on the surface of K-Li4SiO4, indicating the emergence of Ni transfer from Ni/Al2O3 to K-Li4SiO4 during the ICCU-DRM process [32]. Phase compositions of the sorbent and catalyst after 10 cycles was also analyzed by XRD and presented in Fig. 6(c). It can be found that Li4SiO4 is still the main phase in K-Li4SiO4, but there is some LiAlO2 appearing in the Ni catalyst, indicating very slight reaction of Li from the sorbent with Al2O3 in the catalyst during the high temperature contact in ICCU-DRM process. The micro-structural parameters of the fresh Ni/Al2O3 and K-Li4SiO4 and those after 10 cycles are summarized in Fig. 6(c-d) and Table S1 as well. While a reduction of the pores ranging in 4–20 nm is observed of the Ni/Al2O3 catalyst after 10 cycles, the pore size distribution of K-Li4SiO4 is almost the same. Generally, the morphology and phase composition of K-Li4SiO4 sorbent and Ni/Al2O3 catalyst remain basically unchanged after 10 cycles, showing good cyclic stability. But Li and Ni transfer between K-Li4SiO4 sorbent and Ni/Al2O3 catalyst may be another factor affecting their working life.”
“Fig. 6. Materials characterization: (a) SEM-EDS images of K-Li4SiO4 after 10 cycles; (b) SEM-EDS images of reduced Ni/Al2O3 after 10 cycles; (c) XRD patterns of K-Li4SiO4 and reduced Ni/Al2O3 after 10 cycles; (d) pore distribution of fresh Ni/Al2O3 and Ni/Al2O3 after 10 cycles; (e) pore distribution of fresh K-Li4SiO4 and K-Li4SiO4 after 10 cycles.” https://doi.org/10.1016/j.seppur.2021.119476
