Effects of additives on the hydrogen generation of Al–H2O reaction at low temperature

Summary Water displacement method is used to study the influence of temperatures (60–80°C), additives (Na2CO3, NaCl, Na2CO3/NaCl) and concentrations on the reaction characteristics and kinetics of Al–H2O. Results show that the reaction rate and the hydrogen yield are enhanced with the increase of the temperature or by adding Na2CO3. The reaction rate is decreased by adding NaCl, but which has less effect on the hydrogen yield. For the mixture additive, Na2CO3 plays a key role in improving the hydrogen yield and the reaction rate. The influence degree of different factors is analyzed by orthogonal method. The most obvious factor is additive, but additive concentration has a minimum influence. The solid products are collected and analyzed by X-ray diffraction and transmission electron microscopy. Al, Al(OH)3 and AlO(OH) are detected. The spherical particles are obviously found at the initial reaction stage. However, they change to flocs at the end of reaction. Kinetic analysis shows that the reaction mechanism of Al–H2O is changed by adding Na2CO3 or mixture, but it is not affected by adding NaCl. Moreover, the apparent activation energy of Al–H2O is 74.49 kJ mol−1, while it is only 43.03 kJ mol−1 for Al–H2O with 5 wt% Na2CO3 addition. Copyright © 2017 John Wiley & Sons, Ltd.