The assessment of the importance and catalytic role of chromium oxide and chromium carbide for hydrogen generation via hydrolysis of Magnesium

Abstract

Increasing energy demands and low-carbon emission energy carriers are the global challenges for renewable energy resources. Regarding the aforementioned issues, magnesium-based composites are promising candidates for energy carriers. However, rapid initial hydrolysis kinetics and higher hydrogen yields are objectives for practical application. In this study, chromium-based catalysts (Cr2O3, Cr3C2) are employed via ball milling to activate Mg. Finally, we use Mg-Xwt%Y (X=1, 3, 5, and 10, Y= Cr2O3 and Cr3C2)composites to produce hydrogen. In seawater, Mg-10wt%Cr2O3 can produce 798 and 808 mL/g hydrogen, while 821 and 831.6 mL/g are achieved from Mg-10wt%Cr3C2 in seawater and 0.5 M MgCl2 solutions. Additionally, Cr2O3 and Cr3C2 significantly improve the Mg hydrolysis activation energies. However, incorporating Cr2O3 and Cr3C2, the activation energies for the hydrolysis of Mg with seawater are achieved to 19.447 kJ mol-1 and 17.290 kJ mol-1, while they are reduced to 15.69 kJ mol-1 and 14.369 kJ mol-1 with 0.5 M MgCl2 solutions, respectively. In comparison, Mg-10wt%Cr3C2 composite exhibits superior performance, which is attributed to the higher anode potential value of Cr3C2. This work accelerates the hydrolysis kinetics and provides a sufficient technique to produce hydrogen from Mg composite for the application of portable devices.