Enhanced Hydrogen Permeability of Mixed Protonic–Electronic Conducting Membranes through an In‐Situ Exsolution Strategy

Abstract

Mixed protonic–electronic conducting (MPEC) ceramic membranes with high H2 permeability and stability are significant for practical H2 separation. CO2‐tolerant lanthanum tungstate oxides have received much attention, but their low H2 permeability is their main problem for membrane applications. Herein, an efficient in‐situ exsolution strategy is proposed to enhance the H2 permeability and CO2 stability of lanthanum tungstate‐type membranes. During H2 permeation, the catalytic Pd nanoparticles are in‐situ generated from the bulk oxide lattices and dispersed evenly on the membrane surfaces, which greatly promotes the H2 surface exchange kinetics. Also, the protonic conductivity of the membranes is effectively improved through the introduction of Pd. Consequently, the H2 permeation flux is increased by 3.5 times and a maximum H2 flux of 1.3 mL min−1 cm−2 is achieved at 1000 °C through the La5.5(W0.6Mo0.4)0.95Pd0.05O11.25‐δ (LWMPd) membrane. The LWMPd membrane shows outstanding long‐term chemical stability during 300 h continuous operation in a CO2‐containing atmosphere. Therefore, this in‐situ exsolution formation of Pd nanoparticles provides effective guidance for developing competitive MPEC membranes for H2 separation and purification.

Tuning the two phases ratio by nonmetal ion doping in dual‐phase mixed‐conductive ceramic membranes

“…Therefore, the processes in Equations () and () were greatly enhanced with the removal of O 2− , resulting in the most detected H 2 permeation flux. It can be seen that the influence of steam on the H 2 permeation of materials at the sweep side and the feed side was consistent with literature reports 48–50 . Then, the long‐term stability of BCFe and BCFeP 0.05 membranes at 950°C under humidification at the sweep side (condition (i)) was studied, as shown in Figure 4c.…”

“…It can be seen that the influence of steam on the H 2 permeation of materials at the sweep side and the feed side was consistent with literature reports. [48][49][50] Then, the long-term stability of BCFe and BCFeP 0.05 membranes at 950 • C under humidification at the sweep side (condition (i)) was studied, as shown in Figure 4c. Compared to the parent BCFe membrane, the partial conductivity of protons and electrons of the representative BFCeP 0.05 was slightly decreased after the partial substitution of Fe site with P (Figure S12a).…”

Micro-beam XAFS reveals in-situ 3D exsolution of transition metal nanoparticles in accelerating hydrogen separation

“…The anchoring of metal nanoparticles on the grain surface reduces the migration path for electron conduction, enhancing both electron conductivity and catalytic processes. 10,[19][20][21][22][23]33,34 The microscopic morphology of BZCYYbFe powder remained largely unchanged after hydrogen treatment under a reducing atmosphere, indicating the stable presence of Fe within the lattice without any exsolution occurring, as shown in Figure 3C. It has been reported that the exsolution of metallic elements under reducing atmo-spheres is influenced not only by the reducibility of material, but also by the concentration of oxygen vacancies surrounding them; 35 a higher concentration of oxygen vacancies (lower coordination number) tends to promote such exsolution.…”

“…In this study, we investigated the correlation between enhanced hydrogen separation performance and the exsolution of metal nanoparticles. For this purpose, we doped Fe, Co, and Ni elements, known for their catalytic effects, 22 into the B-site of the BZCYYb perovskite structure. This doping aimed to enhance electronic conductivity and promote hydrogen separation.…”

Tantalum doped La0.6Sr0.4FeO3−δ electrodes for symmetrical proton conducting solid oxide fuel cells

“…The solid-state reaction (SSR) method was used for synthesizing LSFT and La 0.6 Sr 0.4 Fe 0.9 Nb 0.1 O 3− δ (LSFN) powders for a low cost and simple preparation process. 27–29 The raw chemical agents used are analytically pure La 2 O 3 , SrCO 3 , Fe 2 O 3 , Ta 2 O 5 and Nb 2 O 5 . BZCYYb powders were prepared by the sol–gel method.…”