Hydrogen generation from pure water using Al-Sn powders consolidated through high-pressure torsion
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Ryo Yonemoto and Makoto Arita Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Fukuoka 819-0395, Japan
Zenji Horita Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Fukuoka 819-0395, Japan; WPI, International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, Fukuoka 819-0395, Japan (Received 27 August 2015; accepted 8 February 2016)
Al–Sn binary alloys are fabricated by powder consolidation using high-pressure torsion (HPT). The HPT-processed samples are immersed in pure water and hydrogen generation behavior is investigated with respect to the imposed strain through the HPT processing at a selected temperature in the range of 297–333 K. Microstructures of HPT-processed alloys are analyzed by x-ray diffraction, transmission electron microscopy (TEM), electron probe microanalysis (EPMA) and electron back scattered diffraction (EBSD) analysis. Results show that it is important to add more than 60 wt% of Sn to activate hydrogen generation from the Al–Sn alloys in pure water. TEM and EBSD images reveal significant grain refinement while EPMA results exhibit homogenous distribution of elements achieved by HPT. The grain refinement and distribution of elements attained by HPT processing influence greatly the hydrogen generation rate and yield of the alloys. An Al–80 wt% Sn alloy with an average grain size of ;270 nm exhibits the highest hydrogen yield and generation rate in pure water at 333 K.
I. INTRODUCTION
Aluminum and its alloys are widely used in various fields, such as transportation, building, electrical engineering, as well as packaging due to their valuable mechanical, electrical, and thermal properties. These applications are well accepted through the stability of oxide film on the aluminum surface spontaneously formed in air or in contact with aqueous solutions, which shifts the corrosion potential of aluminum by nearly 1 V in the positive direction. Thus, aluminum-based materials are normally recognized to have good resistance to corrosion. Such a resistance can be a great advantage for the aluminum used as constructional materials. Another attractive property of aluminum is its standard reversible potential [EAl3þ =Al ¼ 1:66 V (versus standard hydrogen electrode)], which makes aluminum used as anode material in a battery system, and sacrificial anode in cathodic protection of steel in seawater.1–4
Contributing Editor: Xiaobo Chen a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.74
Recently, the use of aluminum and its alloys to produce hydrogen through reaction with water has attracted researchers due to their abundant resource on Earth, high theoretical hydrogen production (1.359 L for 1 g Al at 298 K and 1 atm) and low cost.5–7 In comparison with other hydrogen production methods such as photocatalytic method,8–13 photoelectrocatalytic method,14,15 electrocatalytic method,16–20 thermalcatalytic method,21 and biocatalytic method,22 Wang
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