Site-specific engineering of Pr dopants in BaFeO3–δ perovskites as high-efficiency air electrode for protonic ceramic electrochemical cell

Site-specific doping in perovskite induces distinct defect type and concentration. • Pr doping at A-site of BaFeO 3–δ causes reduced [ V O ⋅ ⋅ ] $V_O^{\cdot \cdot }]$ and basicity. • Pr doping at B-site causes increased [ V O ⋅ ⋅ ] $V_O^{\cdot \cdot }]$ , basicity, and enlarged lattice volume. • B-site Pr-doping enhances the hydration capability and proton diffusivity. • B-site Pr-doping electrode reduces R p and enhances electrode reaction kinetics. Lattice and electron defects, as well as O 2– basicity, in protonic ceramic electrochemical cells (PCECs) play a pivotal role in determining electrode reaction kinetics. Herein, we adopt the same dopant (Pr 3+ ions) to modulate the structure and properties of BaFeO 3–δ via substitution at its A- or B-site, and elucidate the mechanism underlying the performance discrepancy. The rare-earth element Pr 3+ is structurally compatible with both A-site Ba 2+ and B-site Fe 3+ cations, enabling substitution at either site to maintain a stable cubic perovskite structure. Compared to A-site doping (Ba 0.9 Pr 0.1 FeO 3–δ , BPrF), Pr doping at B-site (BaFe 0.9 Pr 0.1 O 3–δ , BFPr) increases oxygen vacancy concentration, elevates O 2– basicity and enlarges lattice volume, which enhance the proton uptake capability and promote the proton transportation. Meanwhile, Pr doing at B-site optimizes the Fe 3d- e g electron filling, which facilitates the charge transfer process. All these favorable effects synergistically boost the electrode reaction kinetics. As a result, the B-site doped BFPr demonstrates a low polarization resistance of 0.264 Ω·cm 2 at 600 °C, approximately half that of the BPrF, achieves an electrolysis current density of 2.19 A·cm⁻ 2 at 1.3 V and a peak power density of 1.02 W·cm⁻ 2 at 700 °C, and displays exceptional operation stability in both EC and FC modes. This work offers valuable insights for rational design of advanced PCEC air electrodes. Download: Download high-res image (209KB) Download: Download full-size image