Microstructure of hierarchical nanoporous copper from electrochemical dealloying of additively manufactured and cast Al–Cu intermetallics

Nanoporous copper (np-Cu) is a cost-effective alternative to nanoporous gold and platinum in heterogeneous catalysis provided that np-Cu has a hierarchical pore structure that interconnect small pores for high surface area-to-volume ratio with large pores for efficient mass transport. Dealloying binary Al-Cu alloys is a promising route to provide np-Cu. Using two differently produced precursor alloys of similar composition, it was investigated whether hierarchical np-Cu can be produced with a similar electrochemical dealloying process. The alloys were either cast (Al-46 wt%-Cu) or in-situ alloyed from a 50:50 (wt%) mixture of aluminum and copper powders using laser powder bed fusion. Both alloys consist of Al 2 Cu and AlCu domains that exhibit distinct, alloy-specific morphologies. Regardless of the precursor alloy, the resulting np-Cu contains less than 0.1% residual Al and is hierarchical with pore sizes in three different diameter ranges, 4- 100 μ m , 40-200 nm, and 2-10 nm. The latter pores are more abundant in np-Cu from the cast alloy. Micro-computed X-ray tomography and scanning electron microscopy reveal domains of different Cu densities being reminiscent in size and shape of the domains in the precursor alloys. Thus, tailoring the phase composition of intermetallic precursor alloys enables simultaneous control of pore sizes between 0.1 and 100 μ m for mass transport and of the local density of np-Cu.