Dispersion and distribution of bimetallic oxides in SBA-15, and their enhanced activity for reverse water gas shift reaction

Abstract

We used the direct hydrothermal synthesis method to obtain various well-dispersed bimetallic oxides/SBA-15 for the first time. It is possible that well-dispersed relatively large bimetallic sulfates are formed during the hydrothermal synthesis process and then re-dispersed with difficulty during the heat treatment process resulting in the formation of well-dispersed oxide particles in SBA-15. TEM elemental maps of CuO–NiO/SBA-15 clearly illustrated that CuO and NiO particles were monodispersed in SBA-15. TEM–EDX line analysis revealed that NiO particles were well distributed on the SBA-15 surface, and then covered by CuO particles. TEM elemental maps of CuO–CeO₂/SBA-15 clearly showed that CuO and CeO₂ particles aggregated slightly in SBA-15. TEM–EDX line analysis showed that CeO₂ particles were well distributed on the SBA-15 surface, and then covered by CuO particles. TEM elemental maps of NiO–CeO₂/SBA-15 clearly illustrated that NiO and CeO₂ particles aggregated slightly in SBA-15. TEM–EDX line analysis revealed that NiO particles were largely mixed with CeO₂ on the SBA-15 surface. Therefore, TEM elemental maps can be used to study the dispersion of bimetallic oxides, and TEM–EDX line analysis is very effective for investigating their distribution in SBA-15. Compared with monometallic oxides/SBA-15, the obtained bimetallic oxides/SBA-15 catalysts exhibited excellent efficiency as regards reducing CO₂ to CO by the reverse water–gas shift (RWGS) reaction. In particular, the bimetallic oxides/SBA-15 catalysts could result in the high CO₂ conversion to CO at low temperature.