Novel Mo/TiN composites for an alkali metal thermal-to-electric converter (AMTEC) electrode

Core-shell composite powders composed of molybdenum (Mo) coated on titanium nitride (TiN) were synthesized using a Pechini-type polymerizable complex method to improve the microstructural stability and electrochemical performance of alkali metal thermal-to-electric converter (AMTEC) electrodes. The coverage of porous Mo shells was controlled by adjusting the concentration of resin-embedded molybdenum sources around TiN particles. Each composite powder was characterized by microstructural analysis (SEM, TEM) and X-ray spectroscopy (XRD, EDX and XPS). During the synthesis process, thin oxide layers (i.e., TiOx, with x=1.0-2.0) were formed on the TiN surface. Each Mo and TiN phase shares a common intermediate oxide layer, and there are strong interactions between oxygen anions and Mo atoms at the interface. As a result, there are cohesive networks between Mo and TiN at the core-shell interface, and these networks control the grain growth of Mo at high temperatures (>700 °C). A single cell composed of Mo/TiN powder (Mo 1.0 mol%) was observed to perform well (180 mW/cm2) and exhibit a low area specific resistance (ASR at 0.7 V) of 0.4 Ωcm2 at 700 °C.