Effect of expanded natural graphite addition and copper coating on reaction kinetics and hydrogen storage characteristics of metal hydride reactors

Experimental and numerical studies are carried out to determine the effects of copper coating and/or ENG (expanded natural graphite) addition on the hydrogen storage performance of ground LaNi5. The amounts of copper coating and/or ENG addition are also investigated. The results reveal that the thermal conductivity of ground LaNi5 can be improved by up to ∼6 and ∼12 times with copper coating and ENG addition, respectively. This results in enhanced hydrogen absorption kinetics thereby significantly reduced hydrogen charging times, compared to those determined for LaNi5 without any addition. On the other hand, the amount of hydrogen stored shows a decreasing trend with increasing copper coating and ENG addition since the weight of storage material loaded to the reactor is kept the same. Nevertheless, the optimum copper and ENG contents are determined regarding the amount of stored hydrogen and the corresponding charging time. Similar H/M values are obtained with the optimized powders with additives compared to that of ground LaNi5. Based on these results, various new samples are also prepared by mixing the decided copper coated LaNi5 and ENG added LaNi5 powders and examined to optimize the composition of these blended powders.