Reviving the activity of Si-contaminated cathodes via chloride anion doping for proton-conducting solid oxide fuel cells

Silicon contaminants, often introduced from raw materials or sealants, severely impair the performance of perovskite cathodes in proton-conducting solid oxide fuel cells (H-SOFCs). To counteract this poisoning effect, this study proposes a chloride anion doping strategy to mitigate the detrimental impact of Si contamination, using La_0.5Sr_0.5FeO₃ (LSF) as a case study. While Si doping increases the oxygen vacancy formation energy and slows oxygen/proton transport in LSF, the co-incorporation of Cl⁻ effectively reverses these adverse changes. Cl doping expands the lattice, promotes charge redistribution, and significantly reduces the energy barrier for vacancy formation. These structural modifications enhance both bulk diffusion and surface exchange kinetics for oxygen and proton species, as confirmed by electrical conductivity relaxation measurements. More importantly, the Cl-Si codoping strategy not only offsets the negative effects of Si contamination but also improves material properties beyond those of contamination-free LSF. As a result, the Cl-doped cathode achieves a peak power density of 1537 mW∙cm⁻² at 700 °C, outperforming even the fuel cell with a pristine LSF cathode. Furthermore, the cell exhibits excellent operational stability. This work demonstrates that purposeful anion doping can effectively alleviate cation-impurity poisoning and offers a viable route toward developing cost-effective and durable cathodes for H-SOFCs.