Hierarchical Bulk Nanoporous Aluminum for On-Site Generation of Hydrogen by Hydrolysis in Pure Water and Combustion of Solid Fuels

There are still many scientific and engineering challenges that need to be addressed before a true sustainable hydrogen economy can be realized. Three of these challenges include sustainable hydrogen generation without CO2 emissions, effective storage of this hydrogen for specific applications, and expanding the limited existing hydrogen infrastructure. Here we demonstrate (i) the fabrication of hierarchical bulk nanoporous aluminum with the coexistence of macroscopic and mesoscopic ligament/pore structures, with the mesoscopic ligaments in the range of 10-20 nm; (ii) the use of this aluminum to produce hydrogen on-site with a yield of similar to 52-90% by hydrolysis with "pure" water, without incorporation of any catalyst or reaction promoter in the aluminum-water system; and (iii) the combustion of this aluminum in air under ambient conditions, which implies that this material could be attractive as a combustion fuel catalyst, e.g., to enhance the ignition and combustion of solid propellants. The inclusion of secondary aluminum or carbon-free primary aluminum in our process will make it possible to produce hydrogen with reduced carbon footprint for on-site and on-board applications using only nanoporous aluminum and water.