An Approach To Enhance the CO₂ Tolerance of Fluorite–Perovskite Dual-Phase Oxygen-Transporting Membrane

Most of the alkaline earth-containing perovskite-based oxygen-transporting membranes (OTMs) have insufficient tolerance toward CO₂ that potentially limits their commercial applications, for example, oxy-fuel combustion processes with CO₂ capture. One concern regarding the chemical potential of oxygen that may influence the CO₂ tolerance of perovskites, however, is lacking effective investigations. In the present work, we demonstrate that the approach to increase the chemical potential of oxygen at the feed side contributes to stabilize the oxygen permeation fluxes of the fluorite–perovskite dual-phase OTM under CO₂-rich atmosphere, and we further verify that oxygen can effectively act as a “buffer” to prevent the carbonate formation. Remarkably, we achieve high and stable oxygen permeation fluxes over 0.84 mL cm^–2 min^–1 during long-term operation at 900 °C with a 0.5 mm thickness 80 wt % Ce_0.8Gd_0.15Cu_0.05O_2−δ-20 wt % SrFeO_3−δ (CGCO-SFO, nominal composition) dual-phase membrane using oxygen-enriched air as the feed gas and pure CO₂ as the sweep gas

Neutral and Cation-Free LTA-Type Aluminophosphate (AlPO₄) Molecular Sieve Membrane with High Hydrogen Permselectivity

Neutral and Cation-Free LTA-Type Aluminophosphate (AlPO4) Molecular Sieve Membrane with High Hydrogen Permselectivit

<i>In Situ</i> Synthesis of MOF Membranes on ZnAl-CO₃ LDH Buffer Layer-Modified Substrates

We develop here a urea hydrolysis method to <i>in situ</i> prepare asymmetric ZnAl-CO₃ layered double hydroxide (LDH) buffer layers with various stable equilibrium morphology on porous Al₂O₃ substrates. In particular it is found that well-intergrown ZIF-8 membranes can be directly synthesized on the ZnAl-CO₃ LDH buffer layer-modified substrates, owing to the specific metal–imidazole interaction between ZnAl-CO₃ LDHs and ZIF-8. Other Zn-based MOF membranes, like ZIF-7 and ZIF-90, can also be synthesized with this method. Our finding demonstrates that LDH buffer layer represents a new concept for substrate modification

Site-Selective Noble Metal Growth on CdSe Nanoplatelets

We report on a synthesis procedure to achieve site-selective growth of noble metal domains on CdSe nanoplatelets. The novel morphological properties of the resulting metal–semiconductor nanoheteroplatelets are characterized by transmission electron microscopy, UV–vis absorption, photoluminescence emission, X-ray photoelectron spectroscopy, and by X-ray diffractometry. By variation of the synthesis parameters, several different morphologies can be achieved: depending on the noble metal and the type of precursor, the growth of Au, Pt, and Pd domain takes place at the corners or edges, around or only at the two shorter edges of the rectangular sheet. This novel kind of hybrid nanoheterostructure might find future applications in photocatalysis, chemical sensing, or fabrication of photovoltaic devices

Tuning the Thermoelectric Performance of CaMnO₃‑Based Ceramics by Controlled Exsolution and Microstructuring

The thermoelectric properties of CaMnO3−δ/CaMn2O4 composites were tuned via microstructuring and compositional adjustment. Single-phase rock-salt-structured CaO–MnO materials with Ca:Mn ratios larger than unity were produced in reducing atmosphere and subsequently densified by spark plasma sintering in vacuum. Annealing in air at 1340 °C between 1 and 24 h activated redox-driven exsolution and resulted in a variation in microstructure and CaMnO3−δ materials with 10 and 15 vol % CaMn2O4, respectively. The nature of the CaMnO3−δ/CaMn2O4 grain boundary was analyzed by transmission electron microscopy on short- and long-term annealed samples, and a sharp interface with no secondary phase formation was indicated in both cases. This was further complemented by density functional theory (DFT) calculations, which confirmed that the CaMnO3−δ indeed is a line compound. DFT calculations predict segregation of oxygen vacancies from the bulk of CaMnO3−δ to the interface between CaMnO3−δ and CaMn2O4, resulting in an enhanced electronic conductivity of the CaMnO3−δ phase. Samples with 15 vol % CaMn2O4 annealed for 24 h reached the highest electrical conductivity of 73 S·cm–1 at 900 °C. The lowest thermal conductivity was obtained for composites with 10 vol % CaMn2O4 annealed for 8 h, reaching 0.56 W·m–1K–1 at 700 °C. However, the highest thermoelectric figure-of-merit, zT, was obtained for samples with 15 vol % CaMn2O4 reaching 0.11 at temperatures between 800 and 900 °C, due to the enhanced power factor above 700 °C. This work represents an approach to boost the thermoelectric performance of CaMnO3−δ based composites