Researchers led by Prof. LI Hui, Prof. CHEN Ping and Associate Professor LIU Lin from the Dalian Institute of Chemical Physics (DICP)
of the Chinese Academy of Sciences demonstrated novel Pd composite membranes with a finger-like and gap structure and their application in NH3
decomposition membrane reactor. Their studies were published in Chem. Eng. J
Due to unique permeability to hydrogen and its isotopes, Pd-based membranes play an important role in ultrapure hydrogen generation in semiconductor industry as well as pure hydrogen production for fuel cell application in both vehicular and stationary scenarios.
The thermal/chemical stability remains the most critical challenge towards the commercial application of Pd-based composite membranes. Under fuel cell application conditions, the fast response requirements during startup/shutdown process further impose a high demand on the stability of Pd composite membranes.
(a) The schematic of novel-configuration Pd composite membrane and NH3 decomposition membrane reactor; (b) A long-term stability test of 200 h of Ru-catalyzed NH3 decomposition Pd membrane reactor at 673 K. (Image by LI Hui and LIU Lin)
This study presented a facile and effective approach to develop high performance stainless-steel supported Pd composite membranes with a finger-like and gap structure by coating the finger-like porous stainless-steel support (PSS) with MnCO3 particles, which formed a small gap of ca. 1 μm during subsequent thermal treatment.
The stability of this novel configuration was demonstrated under 20–50 fast heating up/cooling down cycles at a maximum ramp rate of 10 K/min in near practical fuel cell application conditions.
Such a structure imitates semi-free-standing bulk Pd membranes, which not only avoids the direct contact between Pd layer and PSS and ensures a high H2 permeance, but also avoids the shear stresses between the metal membrane and module.
The membrane with a finger-like and gap structure was applied in NH3 decomposition membrane reactor, which achieved nearly complete NH3 conversion at a relatively low temperature of 673 K and remained stable for 200 h, exhibiting potential in future applications.