Liming Zhang,Shiqing Hu,Zhongwei Cao,Bingjie Pang,Jingyi Wang,Peng Zhang,Xuefeng Zhu,Weishen Yang
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.
A well-intergrown and defect-free tubular KAUST-7 membrane was fabricated via in-situ synthesis assisted by fluorinated molecular building block using green solvent of water on coarse asymmetric α-Al 2 O 3 tubes. The strategy averted the serious corrosion of high-concentration hydrofluoric acid (HF) to α-Al 2 O 3 supports due to the substitution of HF with the pre-synthesized NiNbOF 5 , overcoming the difficulty of serious corrosion to supports compared to traditional one-pot synthesis. The pH manipulation of synthesis solution is proved crucial to the fabrication of defect-free KAUST-7 membranes. In addition, effects of reactant concentration, crystallization temperature and reaction solvents on the morphology and separation performance of KAUST-7 membrane were investigated. The optimized KAUST-7 membrane M4 exhibited a H 2 perm-selectivity of 17.7 over CO 2 for H 2 /CO 2 binary mixture with a H 2 permeance of 2.2 × 10 −7 mol m −2 s −1 Pa −1 at 25 °C and 1 bar, while the H 2 /CO 2 separation factor just had a slight decrease when test temperature increased to 120 °C. The formation mechanism of KAUST-7 membranes via in-situ method in this work was investigated by exposing a bare α-Al 2 O 3 tube into NiNbOF 5 aqueous solution at the pH of 4.0 at 130 °C for 12 h. XPS and FT-IR observations revealed the formation of AlF x O y or AlF x species, which were deduced to be acted as linkers to connect with 2D Ni (II)-pyrazine layers, promoting the heterogeneous nucleation of KAUST-7 crystals on the surface of Al 2 O 3 support.
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