Hydrogen storage in nanostructured carbon-based materials

Zhang, Yinghe (2011). Hydrogen storage in nanostructured carbon-based materials. University of Birmingham. Ph.D.

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Abstract

Attention has been paid to carbon materials for use as hydrogen storage media, as carbon is light and generally of low-cost. Graphite ball-milled in hydrogen for 80 h can subsequently desorb 6 wt% hydrogen. However, the desorption temperature required is relatively high (over 400°C) and some methane is also evolved. Furthermore, it is not reversible (i.e. re-absorption is not possible for pure graphite). To understand the mechanism of hydrogen sorption, the effect of the milling conditions and additions on the microstructure and hydrogen storage properties have been investigated, by: Thermal Gravimetric Analysis - Mass Spectrometry, X-ray Diffraction, Scanning Electron Microscopy, Transmission Electron Microscopy, and Raman spectroscopy.

In this work, graphite was ball-milled in a tungsten carbide pot (3 bar H\(_2\), up to 40 h). By careful control of the duration (10 h) of ball-milling under hydrogen, the optimum formation of nanostructured graphite for pure hydrogen desorption (5.5 wt%, around 400°C), was achieved. Preliminary studies also found that the hydrogen pressure during milling has a significant effect on both the hydrogen content and the desorption behaviour. A graphite-0.5 wt% Fe sample milled for 10 h desorbed the largest amount of pure H\(_2\) (9.6 wt%, at around 350°C). This value is similar to the estimated theoretical value (10 wt% H\(_2\)) and significantly higher than the reported highest values (6.1 wt% desorbed H\(_2\), with CH\(_4\)). Compared with pure graphite, the onset desorption temperature of the 0.5 wt% Fe sample decreased by 50°C; and amount of desorbed H\(_2\) approximately doubled.

An understanding of the relation between microstructure and hydrogen sorption properties is useful for further understanding of the mechanism of hydrogen sorption and improving the hydrogen storage properties.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):