Chemical and mechanical stability of BCZY-GDC membranes for hydrogen separation

This work investigates, for the first time, the hydrogen permeation of BaCeZrYO-CeGdO (BCZY-GDC) asymmetric membranes for 100 h, using wet 15% CO in Ar as sweep gas. In the same frame, ex-situ aging tests were performed for 100 h exposure at 750 °C in different atmospheres (H, CO, H + CO), to evaluate the phase, microstructure, and mechanical long-term stability of this system. The thermal aging in H-atmosphere leads to lower flexural strength caused by a microstructure embrittlement of the BCZY-GDC asymmetric membrane, due to chemical expansion/contraction of the GDC cell after the aging cycle. Indeed, micro-cracking of GDC grains, that decreases the composite hardness, is observed in symmetric (pressed pellet) membranes. The aging in CO causes a slightly increase in flexural strength values due to the formation of sub-micrometric Zr-doped ceria-BaCO phases at the expense of the perovskite. Higher hardness values related to the emerging of BaCO islands on the symmetric membrane surface were also recorded. In H + CO atmosphere (real testing condition), the membrane shows a slight decrease in flexural strength and hardness while no evident morphological or structural changes (except the BaCO formation in traces) were observed. This study highlights that promising and stable hydrogen permeation flux values can be recorded using the asymmetric configuration for 100 h, using wet 15% CO in Ar as sweep gas. Neither structural nor morphological modification of the membrane were detected after the testing.