Enhanced hydrogen generation performances and mechanism of Al-water reaction catalyzed by flower-like BiOCl@CNTs

Abstract

Al-based composites for hydrogen generation possess many advantages like relatively high H2 capacity and low cost, but their application is hindered by the easy formation of alumina membrane on the Al surface. In this work, a novel flower-like BiOCl@CNTs composite has been fabricated firstly, and then introduced into Al powders by ball milling (Al–BiOCl@CNTspowder) or ball milling combining spark plasma sintering (SPS) (Al–BiOCl@CNTsblock). It is found that the flower-like BiOCl@CNTs can significantly promote the H2 generation from Al-water reactions. Moreover, the performance of Al–BiOCl@CNTspowder for H2 generation can be further improved by SPS treatment. The Al-7 wt% BiOCl@CNTsblock exhibits excellent H2 release performance at room temperature with a H2 yield of 1172.9 mL·g−1 and a conversion yield of 92.7% compared with Al-7 wt% BiOCl@CNTspowder (864.9 mL·g−1 and 68.4%). Furthermore, the Al–BiOCl@CNTsblock demonstrates a favorable oxidation resistance, such as a H2 yield of 912.5 mL·g−1 even after being exposed to air for 35 days. The X-ray diffraction (XRD) analysis illustrates the formation of Bi, Bi2O3 and AlCl3in situ can enhance the Al-water reaction. Density functional theory calculation reveals doped Bi or Bi2O3 can promote charges transfer from Al to Bi or Bi2O3. And the doped Bi can enhance the adsorption of H2O on the Al surface to improve H2 generation of the Al–BiOCl@CNTs.