Nanoporous palladium powders are synthesized on milligram to gram scales by chemical reduction of tetrachloro complexes by ascorbate in a concentrated aqueous surfactant at temperatures between - 20 and 30 degrees C. Particle diameters are approximately 50 nm, and each particle is perforated by 3 nm pores, as determined by electron tomography. These materials are of potential value for storage of hydrogen isotopes and electrical charge; producing them at large scales in a safe and efficient manner will help realize this. A slightly modified procedure also results in nanoporous platinum. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.