The effect of expanded natural graphite added at different ratios of metal hydride on hydrogen storage amount and reaction kinetics

Abstract

In this study, metal hydride pellets were formed to accelerate the hydrogen charge/discharge processes. The heat transfer in hydrogen storage material was improved by employing Expanded natural graphite (ENG). The ideal grinding time for LaNi5 material was determined to be 5 h. In the study, LaNi5 alloy was mixed with ENG in 1%, 5%, 10%, and 20% proportions by weight. The amount of hydrogen stored in the reactor by each mixture at 10 bar pressure was measured depending on time. Within the scope of experimental studies, the thermal conductivity coefficient of LaNi5 materials containing 20% ENG by weight was increased by 1380%. Thus, hydrogen charge/discharge processes were accelerated. Storage materials were characterized by XRD and SEM. The thermal conductivity coefficients were measured with the Hot Disk Thermal Constants Analyzer device, and the densities were measured with the Helium Pycnometer device. LaNi5 was chosen as the storage material in the study. It was found that 1–5 wt% ENG addition increased the reaction kinetics without significantly reducing the hydrogen storage capacity in storage alloys. However, in alloys with higher ENG concentrations, the hydrogen storage capacity decreased. The reaction kinetics were increased in the range of 135–260%.