CHENG Yang, ZHOU Yuanjia, LI Xinxin, XIAO Haozhe, GUO Leilei, WU Zhen
AB5-type lanthanum-nickel hydrogen storage alloy is highly promising for engineering applications due to its rapid hydrogen absorption and desorption rates at room temperature. However, large-scale hydrogen production processes, such as fossil fuel reforming and biomass gasification, often introduce impurity gases which can impair the performance of hydrogen storage alloys. To impact of common impurity gases found in hydrogen sources, namely O2, CO2, H2S, N2, CO, H2O, CH4, Ar, and He, on the hydrogen storage characteristics of AB5-type LaNi5 alloys has been investigated. First-principles calculations and pressure-composition-temperature PCT experimental tests were employed to explore the poisoning mechanisms of these impurities on the alloy′s performance, evaluates the adsorption strengths of the impurity gases, and examine the microscopic changes in the electronic structure of the hydrogen storage alloys during poisoning. The results indicate that, compared to hydrogen, O2, CO2, H2S, N2, and CO are preferentially adsorbed onto the material′s surface. Among these gases, O2, H2S, and CO exhibit larger relative adsorption energy values of 2.57 eV, 1.91 eV and 1.21 eV, respectively. Oxygen O2 and hydrogen sulfide H2S undergo dissociative adsorption on the LaNi5 surface. O2 dissociates into O atoms, which adsorb onto the hydrogen absorption active sites. H2S dissociates into SH and H species, which then stably adsorb at the active sites. The remaining gases are adsorbed on the LaNi5 surface in their molecular forms. The effect of impurity gases on the hydrogen storage performance of the alloy was also verified by PCT experimental tests, which showed that CO and O2 deteriorated the hydrogen storage performance of LaNi5 more seriously, with a decrease of 40% and 10%, respectively.
