Dual Roles of Nickel in Key Components of Fuel Cells: Sintering Aid and Electrocatalytic Modifier

The differential effect of nickel doping in perovskite-type energy materials is a focus of SOFC. In this study, the systematic investigation of Sm3+/Ho3+-codoped BaCeO3–BaZrO3 (BaCe0.7Zr0.1Sm0.1Ho0.1O3−δ, BCZSH) revealed the dual-action mechanism of NiO as an electrolyte sintering aid and a cathode active component. In the electrolyte, the doping of 2 mol % NiO can increase the concentration of oxygen vacancies while decreasing ion conduction at grain boundaries in a reducing atmosphere. The symmetrical cell tests show that Ni doping significantly reduces the polarization resistance and activation energy of the Ba0.5Sr0.5Co0.8Fe0.1Ni0.1O3−δ (BSCFN) cathode. DRT analysis confirmed that all dynamic processes were improved. In single cells, internal Ni doping reduced Rp by 44–63% and increased PPD by 54–87% at 600–700 °C. All these indicate that Ni doping can enhance the inherent catalytic activity of the cathode, which accelerates the oxygen reduction reaction (ORR) kinetics.