Controllable hydrogen generation behavior by hydrolysis of MgH2-based materials

Hydrogen supply via the hydrolysis of light-weight metal-based materials is a promising technology for the development of portable hydrogen fuel cells. The hydrolysis reaction of MgH2 with water has been significantly activated through changing the aqueous solution. Special difficulty encountered with these experimental attempts, however, is the lack of satisfactory method to adjust the hydrogen generation rate. In this work, the catalytic activity of typical oxides, hydroxides and chlorides on the MgH2 hydrolyzed in water is systematically investigated, thereby tuning the hydrolysis reaction kinetics of MgH2. It is found that the hydrogen generation rate of the system can be improved dramatically when hydrolyzed in a slightly acidic solution of chloride salts. A mechanism called solution ion effect with consideration both of the anions and cations in the solution is proposed. Such an effect is also found to be strongly correlated to other factors such as the particle size, ion concentration. As consequence, both the hydrogen generation rate and capacity can be well-controlled by tailoring the milling time, concentration of aqueous solutions and the way of introducing solute. Our findings provide new strategies in tailoring the hydrolysis kinetics of light-weight metal hydrides.