Preparation And Properties Of Functional Layer For The Anode Of SOFC Fueled With Hydrocarbon

Coke formation of traditional Ni-based cermets presents a challenging for Solid Oxide Fuel Cells fueled with hydrocarbons. In present work, the Ni-Fe bimetallic functional layer was prepared by thermal decomposition method. The effects of alloying elements, anneal temperature and time, type of chelating agents, and the content of chelating agents on the phase structure and coking resistance of Ni-Fe functional layer were systematically investigated.First, the effect of iron on the phase structure and coking resistance of functional layer was studied. The results show that the coking resistance of nickel can be improved with the addition of iron and the Ni0.75Fe0.25 specimen exhibits the best coking resistance. The single cell with Ni0.75Fe0.25 functional layer delivers a peak power density (PPD) of 326 mW·cm-2, when operating at 650℃ in methane. In addition, the cell with Ni0.75Fe0.25 functional layer experiences a decrease of 9% in voltage after operating for 260 minutes.Second, the effects of anneal temperature and time on the phase structure and coking resistance of Ni0.75Fe0.25 functional layer were evaluated. The coking resistance of the specimen annealed at 705℃ for 1 hour is better than that of species annealed at 675 or 735℃. The cell with functional layer annealed at 705℃ also shows maximum PPD and stability among all cells. The calculation, based on First-principles density functional (DFT) theory, reveals that surface energies of all planes in FeNi3 annealed at 705℃ are lower than that of other samples, contributing to its best coking resistance. In addition, the functional layer annealed at 705℃ for 8 hours has the best coking resistance among all samples annealed for different time.The functional layer with D-gluconic acid exhibits the best coking resistance among all species with different chelating agents, due to its smallest surface energy. In addition, the coking resistance of Ni0.75Fe0.25 layers, with different citric acid contents (molar ratio of CA to metal ions ranges from 0.1 to 1.5), depends on the citric acid contents and CA1.5 has the best coking resistance due to its minimum surface energy of all planes and largest grain size. The cell with CA1.5 functional layer maintains 74% of its voltage after operating for 540 minutes.Finally, the effect of Co on the phase structure and coking resistance of Ni0.75Fe0.25 functional layer were studied. The results show that the phase in ternary system is a FeNi3 related phase.(Ni0.75Fe0.25)0.6Co0.4 shows the best coking resistance among all ternary species.