Effect of Synthesized MgNi4Y Catalyst on Hydrogen Desorption Properties of Milled MgH2

Abstract

It has been reported that ball milling and adding catalyst can improve hydrogen desorption properties of MgH 2. In this study, simultaneous effect of adding catalyst and ball milling on hydrogen desorption properties of MgH 2 was studied. Mechanical alloying and heat treatment methods were used to synthesize MgNi 4 Y intermetallic as a catalyst. In this regard, pure Mg, Ni, and Y elemental powders were ball milled in different conditions and then heat treated at 1073 K (800°C) for 4 hours. XRD and FESEM methods were used to investigate properties of the samples. It was found that, after 10 hours of ball milling and then heat treating at 1073 K (800°C), MgNi 4 Y intermetallic was formed almost completely. The results of Sievert tests showed that as-received MgH 2 did not release any significant amount of hydrogen at 623 K (350°C). But, after ball milling for 10 hours, 0.8 wt pct hydrogen was released from MgH 2 at 623 K (350°C) in 40 minutes. Adding 10 wt pct catalyst via ball milling to MgH 2 led to releasing 3.5 wt pct hydrogen in the same conditions. In addition, increasing ball milling time from 10 to 65 hours increased the amount of released hydrogen from 51 to 85 pct of theoretical hydrogen desorption value and improved kinetic of desorption process.

The synergistic effect of catalysts on hydrogen desorption properties of MgH2–TiO2–NiO nanocomposite

“…While MgH 2 desorbed nothing after 2500 s, the BMM sample desorbed 1.10 wt% of hydrogen starting after 642 s with a slow rate within the first 200 s, as shown in Figs. 6 and 7, which is in good agreement with previous studies [47,48]. For example, Chitsazkhoyi et al [47] claimed that after 30 h of ball milling, pure MgH 2 released about 1 wt% of hydrogen.…”

“…6 and 7, which is in good agreement with previous studies [47,48]. For example, Chitsazkhoyi et al [47] claimed that after 30 h of ball milling, pure MgH 2 released about 1 wt% of hydrogen. In that research, all the samples which had been ball milled for less than 30 h, released less than 1 wt% of hydrogen.…”