Repeatable preparation of defect-free electrolyte membranes for proton-conducting fuel cells

Proton-conducting ceramic cells are promising devices for high-efficient energy conversion, while the preparation of defect-free electrolyte membranes is difficult and blocks their quick development. Here, a vacuum-assistant dip-coating method is developed to prepare defect-free BaCe 0.4 Zr 0.4 Y 0.1 Yb 0.1 O 3-δ (BCZYYb4411) proton-conducting electrolyte membranes on porous anode (40 wt%BCZYYb4411 - 60 wt%NiO) substrates. Unlike the conventional dip-coating process, by using the vacuum-assistant dip-coating method, defects (like running through pinholes, cracks) that would cause gas leakage, short-circuit and low open-circuit voltage (OCV) in following electrochemical tests can be eliminated. By tuning the mass concentration of electrolyte powders in the coating slurry, thin electrolyte membranes with different thicknesses can be reproducibly prepared. Proton-conducting fuel cells (PCFCs) with BaCo 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3-δ (BCFZY0.1) cathode show high OCV values closing to the theoretical value of 1.13 V at 600 °C, demonstrating that dense and defect-free electrolyte membranes are fabricated. The as-prepared PCFC with a 10-μm-thickness defect-free electrolyte membrane shows a high peak power density reaching up to 761 mW cm −2 at 650 °C and stability of more than 250 h at the current density of 200 mA cm −2 at 600 °C. All these results illustrate that the developed method is feasible to prepare dense and thin electrolyte membranes without defects for proton-conducting ceramic cells.