The effects of bismuth and tin on the mechanochemical processing of aluminum-based composites for hydrogen generation purposes

Abstract

The work described in this paper forms part of a study on the mechanochemical processing of Al with dissimilar metals for hydrogen generation purposes. Here, in an effort to contain the cost of the activation of Al, we have excluded use of the expensive precious metal In as an activation compound. Specifically, we describe the microstructural properties and hydrolysis reactivities of activated Al-Bi-Sn composites. Binary and ternary Al, Bi, and/or Sn composites were fabricated using a high-energy mechanochemical processing route and their reactivities towards pure water under standard ambient conditions were determined. Scanning electron microscopy analysis indicated that Bi and Sn intruded the Al particles, resulting in continuous galvanic interaction between anodic Al and cathodic Bi/Sn during hydrolysis reactions. Several composites containing 5 and 10 wt % activation compounds had >95% hydrogen yields. X-ray diffraction analysis indicated that the major phases detected were Al, Bi, and Sn, which suggests that intermetallic phases do not govern morphology changes and hydrolysis reactivity. Bi and Sn could be partially recovered from hydrolyzed Al using H2SO4 and HNO3, respectively.