Hydrogen from waste metals: Recent progress, production techniques, purification, challenges, and applications

In this work, hydrogen production from metals, specifically metal waste (scrap metal), is discussed based on a literature review of recently published research. Hydrogen production from scrap aluminum, magnesium and zinc is broken down into details, providing context on their overall processes, and advantages and disadvantages. Moreover, conventional hydrogen production methods are presented, to provide a baseline for comparison. It was shown that hydrogen production from metal waste had a 70 % hydrogen yield from magnesium due to its high specific energy density, which gives magnesium an edge in hydrogen production within the context of scrap metal. Additonally, aluminum-based alloy powders showed a hydrogen yield of ∼98 %, whereas zinc-based hydrogen production showed relatively low conversion rates bordering ∼20 %. Furthermore, purification techniques that enhance the quality of the produced hydrogen, such as pressure swing adsorption, cryogenic distillation and novel membrane-based, which have shown performnace enhancements compared to their predecessors, are discussed. Finally, economic, technical and social limitations that hinder the progression of hydrogen production from metal waste, as well as the applications and future perspectives, which include on-board hydrogen production and combustion, fuel cells and the chemical industry, are showcased.