Enhancing the Electrochemical Performance of Perovskite-Like Ruddlesden–Popper Oxide Pr 2 NiO 4 through a Gd-Doping Strategy

This study investigates the synergistic optimization of structural stability and electrochemical performance in Gd 3+ -doped Pr 2– x Gd x NiO 4 ( x = 0–0.150) Ruddlesden–Popper (R–P) oxides. Phase analysis coupled to this confirmed that the materials retained the K 2 NiF 4 -type R–P structure. Thermal expansion analysis demonstrated that Pr 1.9 Gd 0.1 NiO 4 possesses an average linear thermal expansion coefficient (TEC) of 12.62 × 10 –6 K –1, showing excellent interfacial compatibility with a gadolinium-doped ceria (GDC) electrolyte. Electrochemical characterization revealed that the symmetric cell Pr 1.9 Gd 0.1 NiO 4 |GDC|Pr 1.9 Gd 0.1 NiO 4 achieved a low area-specific polarization resistance ( R p ) of 1.40 × 10 –2 Ω cm 2 at 800 °C in air, with an oxygen reduction reaction (ORR) activation energy ( E a ) of 0.8 eV. The single cell (NiO–GDC|GDC|Pr 1.9 Gd 0.1 NiO 4 ) delivered a maximum power density of 0.74 W cm –2 at 800 °C and maintained stable operation for 100 h under 0.30 A cm –2 . These results highlight the effectiveness of A-site Gd 3+ doping in enhancing the electrochemical performance and durability of Pr 2 NiO 4 -based cathodes, providing critical insights for developing solid oxide fuel cells.