Abstract
A significant drawback to ammonia borane as a hydrogen storage material is the production of ammonia gas during hydrolysis. As a possible solution, maleic acid is shown to be capable of fully promoting hydrolysis of ammonia borane while also preventing ammonia release in excess of single digit parts per million. The reaction is shown to be relatively insensitive towards common water contaminants, with seawater, puddle water, and synthetic urine resulting in hydrogen evolution comparable to that observed when using highly pure deionized water. A common cola beverage was also investigated as a potential water source, with results deviating from those observed when using the other water sources. The ability to use low quality water sources presents the option of acquiring water at the point of use, greatly increasing the energy density of the system during transportation. For each of the water sources being used, concentrations of ammonia in the gas products of maleic acid-promoted hydrolysis were found to be less than the lower detection limits of the employed analysis methods. Based on this reaction, a portable hydrogen reactor is reported and shown to be capable of on-demand hydrogen generation sufficient to power a proton exchange membrane fuel cell at varying loads without significant changes in system pressure. The overall power production system has substantial value in scenarios where electrical power is required but there is no access to an established electrical utility, with prime examples including disaster relief and expeditionary military operations.
Highlights
Over the course of several decades, ammonia borane has been extensively investigated as a hydrogen storage material for various applications
The results of this study can be categorized into two parts, the first serving to validate that highly pure hydrogen gas can be evolved from organic acid-promoted hydrolysis of ammonia borane when using low-quality water sources, and the second being the demonstration of a system which is built
The results of this study can be categorized into two parts, the first serving to validate that highly pure hydrogen gas can be evolved from organic acid-promoted hydrolysis of ammonia borane when using low-quality water sources, and the second being the demonstration of a system which is built on this concept with many real-world applications in mind
Summary
Over the course of several decades, ammonia borane has been extensively investigated as a hydrogen storage material for various applications. There are multiple methods for releasing hydrogen from ammonia borane, with hydrolysis being advantageous for portable applications because it can be conducted at room temperature and can be scaled to meet a wide range of hydrogen consumption rates. Because ammonia borane is relatively stable in water, a reaction promoter or catalyst is necessary to facilitate hydrolysis at a useful rate [1,2,3]. Many metal catalysts have been reported as being highly active for ammonia borane hydrolysis, with rapid hydrolysis being observed in acidic solutions. In 1979, Kelly and Marriot proposed two mechanisms to describe potential routes by which an acidic solution could promote hydrogen release from ammonia borane [4].
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