Initial oxidation of nano-aluminum particles by H2O/H2O2: Molecular dynamics simulation

• Published in: International journal of hydrogen energy 2021-01, Vol.46 (1), p.1234-1245
• Main Authors: Dong, Rui-Kang, Mei, Zheng, Zhao, Feng-Qi, Xu, Si-Yu, Ju, Xue-Hai
• Format: Article
• Language: English
• Subjects: H2 generation; Hydrogen peroxide and water; Molecular dynamics; Nano-Al; ReaxFF
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2020.09.164

Molecular dynamics simulations on the reactions of nano-aluminum, water with different proportions of hydrogen peroxide were performed by ReaxFF. The reaction rate of the system increases by 27% as the molar ratio of H2O2 increases from 0 to 30%. The reaction paths in each period are elucidated by the change of the numbers of reactants and products. The reaction absorbs heat and releases isolated H atoms in the initial stage through pathways Al + 3H2O → Al(OH)3 + 3H and 3Al + 2H2O → 2AlO + AlH3 + H. Subsequently, H2O2 decomposes and releases O2 through 2H2O2 → 2H2O + O2 as the temperature rises to 350 K. And these O2 are rapidly involved in the formation of Al2O3, corresponding to the process 4AlO + O2 → 2Al2O3 and 2Al(OH)3 + 2AlH3 + 3O2 → 2Al2O3 + 6H2O. In the final stage, H2 molecules generated in accordance with the pathways of Al(OH)3 + AlH3 → Al2O3 + 3H2 and 2AlH3 + 3H2O → Al2O3 + 6H2. Particularly, the production of H2 decreases by 28.2%, 49.8% and 68.6%, as the molar ratio of H2O2 increases from 0 to 10%, 20% and 30%, respectively. Meanwhile, the reaction of Al/H2O/H2O2 releases much more energy (271.40–440.53 kJ/mol) than that of Al/H2O (180.67 kJ/mol). Moreover, the ignition temperature decreases with the increase of H2O2 concentration, but is proportional to the heating rate of ignition. When the molar ratio of H2O2 increases from 0 to 30%, the adiabatic flame temperature of the mixture increases linearly from 2400 K to 3000 K according to the adiabatic simulation. •The evolutions of energy and species along the reaction process were explored.•The addition of H2O2 increases the energy released and decreases the energy barrier.•The addition of H2O2 increases the combustion temperature but drops the ignition point.•The presence of oxide layer causes a reduction in the energy released by the mixture.