TPR studies on NiO–CGO composites prepared by combustion synthesis

NiO–ceria composites, which are promising candidates as anodes for intermediate temperature solid oxide fuel cells (IT-SOFCs) were prepared by urea combustion synthesis (UCS) method. The UCS method is, in general, a highly suitable synthesis method for the production, at low temperatures, of fine and reactive powders. By means of XRD and SEM-EDX techniques, the structural, microstructural and compositional behavior of the as-prepared powders has been studied. In addition, temperature programmed reduction (TPR) tests were performed to investigate the reducibility of the composites. After reduction of the NiO–CGO as-prepared compositions, the combustion powders exhibit the presence of Ni, the fluorite CGO solid solution that remains stable and NiO is no longer present. The morphology and size of the nanoparticles and aggregates of the as-prepared powders make them reactive at intermediate temperatures (400–800 °C). TPR tests show wide overlapping peaks which are associated with the two primary reduction stages; one is related to the surface NiO reduction mechanism and the other to the coexistence of interactions between the NiO–CGO surface and bulk reduction processes. Further, after TPR measurements the resulting products have high phase stability and reproducibility.