Thermally stable nanoporous palladium alloy powders by hydrogen reduction in surfactant templates

Nanometer-scale pores in metals used for hydrogen storage are expected to facilitate mass transport in the materials – in particular, the release of helium decay products when tritium is stored. Scalable methods for production of bulk powders of nanoporous metals typically use chemical reducing agents that can leave impurities in the product. Hydrogen gas can be used as the reducing agent in such procedures. This not only improves purity, but also expands the range of accessible pore and particle sizes and particle compositions. Powders of nanoporous palladium and its alloys with rhodium are synthesized by chemical reduction of chloride complexes by hydrogen in a concentrated nonionic aqueous surfactant at room temperature. Particle diameters are typically several micrometers and each particle is perforated by 2–3 nm pores, as determined by electron microscopy and nitrogen porosimetry. Alloys show major improvement in thermal stability and pore regularity compared to pure palladium. In addition to facilitating heavier isotope storage, the high surface areas of these materials may allow development of metal hydride batteries with high power density.