Ball-Milled and Acid-Treated Mineral Activated Carbon as Hydrogen Storage Material

Abstract

For several decades, carbon allotropes, including graphitic nanofibres and other nanostructures, have been studied as hydrogen storage materials. In this paper, activated mineral carbon (bituminous) was used for the hydrogen storage process. For 3 h, the carbon particle size was continuously reduced by mechanical milling, and the carbon was subsequently refluxed with concentrated nitric acid. Microstructural characterisation and evaluation of the hydrogenation behaviour of the chemically treated and milled mineral were performed. Hydrogen adsorption/desorption experiments were carried out using two methods: the first one using a thermogravimetric analysis (TGA) system with a hydrogen atmosphere during the process of adsorption and nitrogen as carrier gas in the desorption and the second method of hydrogenation was performed in the microreactor (MR) varying pressure, temperature and contact time. On the other hand, ten cycles of adsorption/desorption of hydrogen were performed with each method. The qualitative analysis for hydrogen identification was carried out with a gas chromatograph and the same thermogravimetric analyser with nitrogen used as the carrier gas. The hydrogen absorption capacity in powder samples was 0.45±0.01 and 1.38±0.05 wt% hydrogen in the TGA system and in the MR respectively, according to these results the best method for hydrogen adsorption was using the MR because the pressure applied was higher.