Methane decomposition to produce hydrogen and carbon nanomaterials over costless, iron-containing catalysts

In this work, a series of iron-containing materials (not laboratory-synthesized but from natural, industrial raw materials, by-products or wastes), such as iron concentrate powder, fine/coarse ash and steel slag from steel plants and volcanic mud powder, were investigated as catalysts for methane decomposition. These catalysts exhibited relatively good methane conversion under the following conditions: 2.0 g of catalyst, 50 mL/min CH4, 900 °C for 5 h, even without hydrogen pre-reduction. Fe2O3 species on these samples were found to be gradually reduced by methane to Fe3O4, FeO and then finally into Fe0 active species. When methane decomposed onto the Fe0 active sites, Fe3C species would form to deposit graphite around themselves to finally form carbon nanomaterials, showing possible application in the oxygen evolution reaction and in Li-ion batteries as anode electrodes. Furthermore, using the best catalyst, iron concentrate powder, the effect of temperature and gas hourly space velocity was studied, where 900 °C and 3 L/gcat·h were determined as the optimized reaction conditions to reach the highest carbon/hydrogen yield.