Control of both particle and pore size in nanoporous palladium alloy powders

•Spherical, uniformly sized copper particles are formed by chemical reduction.•Reaction with a palladium salt and a surfactant yields a nanoporous Pd alloy.•Particle size is defined in the first step. Pore size is defined in the second step.•Product retains useful hydrogen storage properties.

Energy storage materials often involve chemical reactions with bulk solids. Porosity within the solids can enhance reaction rates. The porosity can be either within or between individual particles of the material. Greater control of the size and uniformity of both types of pore should lead to enhancements of charging and discharging rates in energy storage systems. To control both particle and pore size in nanoporous palladium (Pd)-based hydrogen storage materials, we have first created uniformly sized copper particles of about 1 μm diameter by the reduction of copper sulfate with ascorbic acid. In turn, these were used as reducing agents for tetrachloropalladate in the presence of a block copolymer surfactant. The copper reductant particles are geometrically self-limiting, so the resulting Pd particles are of similar size. The surfactant induces formation of 10 nm-scale pores within the particles. Some residual copper is alloyed with the Pd, reducing hydrogen storage capacity; use of a more reactive Pd salt can mitigate this. The reaction is conveniently performed in gram-scale batches.

Graphical abstractWe use spherical copper particles to produce micrometer-scale spherical nanoporous palladium particles with high uniformity. A magnified image in the graphical abstract shows the highly porous surface of the palladium metal that is a result of controlled reaction parameters.Figure optionsDownload full-size imageDownload as PowerPoint slide