One of the major obstacles to the widespread use of hydrogen as an energy carrier, especially for... more One of the major obstacles to the widespread use of hydrogen as an energy carrier, especially for transportation applications, is the lack of safe and efficient means for hydrogen storage. Decades of extensive efforts on metal/alloy hydrides, nanostructured carbon materials, and complex hydrides have not led to a viable system that can reversibly store over 6 wt % hydrogen at a moderate temperature range. Recently, irreversible hydrogen storage via catalyzed hydrolysis or thermolysis of chemical/metal hydrides has emerged as an alternative and more promising solution for on-board hydrogen storage. 6] Among the hydride materials of interest, ammonia borane (NH 3 BH 3 , AB) is a leading candidate, which is justified by its extremely high gravimetric hydrogen capacity (19.6 wt %) and relatively favorable thermal stability. AB can release hydrogen via catalyzed hydrolysis in an aqueous solution, [8] catalyzed dehydrocoupling under non-aqueous conditions, or thermolysis at elevated temperatures. [13][15] Compared to the solid-liquid reaction systems, the latter solid-gas approach is clearly more appreciated for practical on-board applications owing to the ease of apparatus design and the hydrogen capacity advantage. However, its practical application is greatly restricted by the sluggish decomposition kinetics at 100 8C and the concurrent release of volatile byproducts (e.g., borazine) that are detrimental for fuel cell operation. [15] Aiming at solving these problems, recent studies focused on developing a nanoengineering strategy [15] and identification of effective catalysts. These efforts have made some progress in improving the H 2 release kinetics and suppressing the generation of volatile byproducts. However, the utilization of structure-directing agents imposes a penalty on hydrogen capacity to levels that are unacceptable for practical application. [15] The identified transition metal catalysts seem problematic for eliminating the detrimental gas impurities, especially at a normal heating rate. Here, we report a very simple and highly effective method for destabilizing AB for high-capacity, high-purity hydrogen generation. By mechanically milling an AB/LiH mixture in a 1:1 molar ratio, the produced material can release over 7 wt % (on a material basis) pure hydrogen at around 100 8C, free of gas impurities. These findings offer a clear potential for using destabilized AB and related materials as high-capacity hydrogen sources for transportation applications.
One of the major obstacles to the widespread use of hydrogen as an energy carrier, especially for... more One of the major obstacles to the widespread use of hydrogen as an energy carrier, especially for transportation applications, is the lack of safe and efficient means for hydrogen storage. Decades of extensive efforts on metal/alloy hydrides, nanostructured carbon materials, and complex hydrides have not led to a viable system that can reversibly store over 6 wt % hydrogen at a moderate temperature range. Recently, irreversible hydrogen storage via catalyzed hydrolysis or thermolysis of chemical/metal hydrides has emerged as an alternative and more promising solution for on-board hydrogen storage. 6] Among the hydride materials of interest, ammonia borane (NH 3 BH 3 , AB) is a leading candidate, which is justified by its extremely high gravimetric hydrogen capacity (19.6 wt %) and relatively favorable thermal stability. AB can release hydrogen via catalyzed hydrolysis in an aqueous solution, [8] catalyzed dehydrocoupling under non-aqueous conditions, or thermolysis at elevated temperatures. [13][15] Compared to the solid-liquid reaction systems, the latter solid-gas approach is clearly more appreciated for practical on-board applications owing to the ease of apparatus design and the hydrogen capacity advantage. However, its practical application is greatly restricted by the sluggish decomposition kinetics at 100 8C and the concurrent release of volatile byproducts (e.g., borazine) that are detrimental for fuel cell operation. [15] Aiming at solving these problems, recent studies focused on developing a nanoengineering strategy [15] and identification of effective catalysts. These efforts have made some progress in improving the H 2 release kinetics and suppressing the generation of volatile byproducts. However, the utilization of structure-directing agents imposes a penalty on hydrogen capacity to levels that are unacceptable for practical application. [15] The identified transition metal catalysts seem problematic for eliminating the detrimental gas impurities, especially at a normal heating rate. Here, we report a very simple and highly effective method for destabilizing AB for high-capacity, high-purity hydrogen generation. By mechanically milling an AB/LiH mixture in a 1:1 molar ratio, the produced material can release over 7 wt % (on a material basis) pure hydrogen at around 100 8C, free of gas impurities. These findings offer a clear potential for using destabilized AB and related materials as high-capacity hydrogen sources for transportation applications.
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Papers by Max Wang