Synergistically enhanced anode performance of PrBaMn₂O_5+δ for proton ceramic fuel cells via nickel doping and exsolution

Proton ceramic fuel cells (PCFCs) are considered highly efficient energy conversion devices, yet their performance is strongly governed by the catalytic activity and stability of anode materials. Although PrBaMn₂O_5+δ (R-PBM) has demonstrated intrinsic tolerance to hydrocarbon fuels, its electrochemical activity at intermediate and low temperatures remains insufficient for practical reversible PCFCs (r-PCFCs) applications. Therefore, a Ni-doped R-PBM anode material, PrBaMn_1.95Ni_0.05O_5+δ (R-PBMN), was studied in this work. The in situ exsolution of Ni nanoparticles after partial Ni substitution for Mn sites significantly improved the anode activity. The exsolved Ni nanoparticles effectively lower the activation energy for C-H bond cleavage, thereby enhancing methane activation and decomposition. Meanwhile, the R-PBMN lattice provides intrinsic hydrophilicity and high proton mobility, which enable cooperative CH₄/H₂O activation and facilitate the formation of CH_xOH* intermediates that suppress carbon deposition. As a result, R-PBMN exhibits substantially enhanced electrochemical performance. At 650 ℃, R-PBMN demonstrated substantially lower polarization resistance than R-PBM: 0.56 Ω cm² in H₂ and 3.38 Ω cm² in CH₄, representing a 90% and 55% reduction, respectively, while retaining a high impedance stability for 120 h in methane-steam atmosphere. At 700 ℃, the peak power density of R-PBMN in H₂ and CH₄ reached 0.82 W cm^-2 and 0.64 W cm^-2, respectively, a 15.5% and 18.5% increase compared to R-PBM. Furthermore, the R-PBMN anode retained the intrinsic coking resistance of the Pr_0.5Ba_0.5MnO_3-δ (PBM) framework, ensuring stable operation for 100 hours in a 50% H₂O/CH₄ atmosphere. This work highlights a cooperative design strategy that transforms PBM from a hydrocarbon-tolerant but low-activity oxide into a high-performance PCFC anode with balanced activity and durability.