Abstract
Chemical doping of ceramic oxides may provide a possible route for realizing high-efficient oxygen transport membranes. Herein, we present a study of the previously unreported dual-phase mixed-conducting oxygen-permeable membranes with the compositions of 60 wt.% Ce0.85Pr0.1M0.05O2-δ-40 wt.%Pr0.6Sr0.4Fe0.8Al0.2O3-δ (M = Fe, Co, Ni, Cu) (CPM-PSFA) adding sintering aids, which is expected to not only improve the electronic conductivity of fluorite phase, but also reduce the sintering temperature and improve the sintering properties of the membranes. X-ray powder diffraction (XRD) results indicate that the CPM-PSFA contain only the fluorite and perovskite two phases, implying that they are successfully prepared with a modified Pechini method. Backscattered scanning electron microscopy (BSEM) results further confirm that two phases are evenly distributed, and the membranes are very dense after sintering at 1275 °C for 5 h, which is much lower than that (1450 °C, 5 h) of the composite 60 wt.%Ce0.9Pr0.1O2-δ-40 wt.%Pr0.6Sr0.4Fe0.8Al0.2O3-δ (CP-PSFA) without sintering aids. The results of oxygen permeability test demonstrate that the oxygen permeation flux through the CPCu-PSFA and CPCo-PSFA is higher than that of undoped CP-PSFA and can maintain stable oxygen permeability for a long time under pure CO2 operation condition. Our results imply that these composite membranes with high oxygen permeability and stability provide potential candidates for the application in oxygen separation, solid oxide fuel cell (SOFC), and oxy-fuel combustion based on carbon dioxide capture.
Highlights
The oxygen transport membranes (OTMs) with high CO2 tolerance have great prospects to be used in oxy-fuel combustion integrated with CO2 capture, which provides an effective way to minimize the emission of CO2 and toxic NOx pollutants from the fossil-fuel power station [17,18,19]
We further investigated the microscopic morphologies and chemical compositions of the sintered membranes by several characterizations including scanning electron microscopy (SEM, Quanta 400F, Oxford), energy dispersive X-ray spectroscopy (EDXS), and backscattered scanning electron microscopy (BSEM)
Oxygen permeation fluxes through the 60 wt.%Ce0.85Pr0.1M0.05O2-δ-40 wt.%Pr0.6Sr0.4 Fe0.8Al0.2O3-δ (M = Fe, Co, Ni, Cu) (CPM-PSFA) composite membranes were explored by a homemade high-temperature oxygen setup connected to a gas chromatograph (GC, Zhonghuida-A60, Dalian, China), as reported in the previous literatures [43,44]
Summary
There has long been interest in ceramic mixed-conducting oxygen transport membranes (OTMs) technology in virtue of their widespread applications in the energy catalytic fields such as air separation [1,2,3,4], cathodes in solid oxide fuel cells (SOFCs) [5,6], hydrocarbons conversion [7,8,9], hydrogen separation/production [10,11,12,13], and oxy-fuel combustion for CO2 capture [14,15,16,17,18]. The OTMs with high CO2 tolerance have great prospects to be used in oxy-fuel combustion integrated with CO2 capture, which provides an effective way to minimize the emission of CO2 and toxic NOx pollutants from the fossil-fuel power station [17,18,19] In this regard, among the mixed-conducting OTMs, recent attention to the development and application of dual-phase membranes has been growing exponentially due to their superior chemical and physical stability compared with the single-phase OTMs. The earliest discovery of dual-phase membranes was using noble metals as the electron-conducting (EC) phases and ceramic perovskite oxides as the pure oxygen ion-conducting (OIC) phases [20]. The aim of the work will focus on the study of the effect of doping Fe, Co, Ni, and Cu transition metals into CP phase on the oxygen permeability and stability
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