Scalable Fabrication of Hierarchically Porous Coating Surface via Microparticle Dealloying and Cold Spray

Due to their locally high surface-to-volume ratio, nanoporous structures exhibit enhanced catalytic activity, superior chemical properties and tailored electromagnetic wave scattering compared to bulk and micrometer-scale metals. Active sites on terminal surfaces, such as kinks, corners, edges, steps, and local facets, possess unique coordination environments and electronic structures, resulting in varied adsorption energies, geometries, absorption and activation barriers. However, a significant fundamental challenge remains: developing a cost-effective and scalable process that is compatible with diverse materials. Current methods are often energy-intensive, involve complex process control, are difficult to scale, require hazardous chemicals that are hard to manage for large surfaces, and typically involve slow, multi-step procedures.

The present study proposes a novel, facile, two-step, and scalable approach that combines microparticle chemical dealloying with solid-state deposition via the cold gas dynamic spray (CGDS) process. Microparticles are environmentally friendly and can be easily collected and recycled. Selective dealloying produces hierarchically porous and compositionally heterogeneous microparticles, incorporating nanoscale termination motifs that provide unrestricted intrinsic access to structure-sensitive behavior while minimizing handling and health concerns.

In this study, Cu₆₀Al precursor microparticles are chemically dealloyed in an electrolytic solution, selectively leaching aluminum to form a bicontinuous, complex copper network. The resulting nano- and micro-porous precursor particles are then deposited using the CGDS process, which preserves their surface features while simultaneously producing additional surface patterning. This approach is compared with post-deposition dealloying of sprayed alloy coatings, with discussion focusing on surface feature size, geometry, structural complexity, and suitability for industrial applications.