(336c) Thermal Stability of Nanopores in Palladium Alloys and Their Hydrides

Nanoporous material architectures can offer improved charging and discharging kinetics in metal hydrides due to their high surface area. We have synthesized nanoporous palladium and palladium alloy powders in a scalable fashion by reduction of palladium salts in a concentrated aqueous surfactant. Particle diameters are micrometer-scale, and each particle is perforated by 3 nm pores. In pure palladium, the pores are unstable at 150 C, but when alloyed with rhodium, they are stable up to 400 C on short timescales. These results are expected to be related to pore lifetime at more moderate temperatures. Electron tomography and elemental mapping after in situ or ex situ heating and hydrogen exposure help us understand the mechanism of the improvement. We observe surface segregation of the minor component in alloys. Pore density and stability are also related to the microstructure of the material. Improved stability can be obtained with minimal sacrifice of hydrogen storage properties.