Morphological Tuning of Nanoporous Metals Prepared with Conversion Reaction Synthesis via Thermal Annealing

Conversion reaction synthesis, namely, reacting an organolithium reducing agent with a metal chloride to produce a metal/LiCl nanocomposite and then removing lithium chloride with a polar organic solvent, is an efficient and scalable way to fabricate a variety of three-dimensional, bicontinuous nanoporous transition metals. Thermal annealing was investigated as a means to tune the morphology of these nanoporous metals. X-ray diffraction studies were used to investigate the effect of thermal annealing on the size and strain of phases in Cu/LiCl, Co/LiCl, and Fe/LiCl nanocomposites, while electron microscopy and nitrogen adsorption studies were used to study the porosity and surface properties of the resulting nanoporous metals after LiCl was removed from the annealed nanocomposites. Annealing metal/LiCl nanocomposites resulted in the controlled growth of the metal nanoparticles, the rate of which depended on the diffusivity of the metal. It was observed that annealing nanocomposites produced more robust nanoporous metals with increased porosity under certain conditions. Overall, it was found that annealing the as-formed nanocomposites rather than the isolated nanoporous metals provides finer control of the conversion synthesis process and allows for the design of more optimized pore structures and thus enhanced suitability for catalytic and electrochemical applications.