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The hydrogen storage properties of nanoporous Pd fabricated by dealloying a Pd0.2Co0.8 alloy were investigated by measuring pressure−composition isotherms (PCTs). The hydrogen storage behaviors of nanoporous Pd were obviously different from those of bulk Pd and other nanostructured Pd materials, such as nanocrystalline Pd and nanoparticle Pd. The miscibility gap narrowed similarly to that in nanocrystalline or nanoparticle Pd, but the gap narrowed in a different manner; that is, the hydrogen dissolution in the α-phase of nanoporous Pd was similar to that in the α-phase of bulk Pd, while that in the β-phase of nanoporous Pd was similar to that in the β-phase of the nanostructured Pd. High-resolution transmission electron microscopy showed lattice disorder (both expansion and contraction) at the surface of nanoporous Pd. First-principles calculations within the generalized gradient approximation suggest that the lattice expansion and contraction are responsible for the hydrogen adsorption in the α-phase of nanoporous Pd.

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We report a simple and spontaneous synthesis of a nanoporous gold prism microassembly with highly dense skins, which is achieved just by immersing nanoporous gold into concentrated hydrochloric acid. The ligament size was coarsened to several hundred nanometers, but the crystal face orientation was still preserved. The same trends were seen in the case of coarsening by annealing; however, the morphology of the nanoporous gold prism microassembly was significantly different from the annealed nanoporous gold.

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The thermal coarsening of nanoporous Au was examined and compared with the thermal instability of Au nanoparticles. The nanoporous Au was coarsened at temperatures far below the melting temperature of Au nanoparticles, which possess sizes similar to the nanoligaments. Differential scanning calorimetry characterization of nanoporous Au exhibited an exothermal peak around 470 K. These results suggest that solid-state process like recrystallization, rather than melting, is responsible for the thermal coarsening of nanoporous Au.

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