Promoting Effects of Anions on Hydrogen Storage Reactions of Li-N Based Materials

Michigan Technological University, Houghton MI

Investigators

Abstract

0931587 Hu One important material for hydrogen storage is lithium imide (Li2NH) because it can reversibly absorb as much as 6.5wt% hydrogen, via the reaction Li2NH + H2 = LiNH2 + LiH. However, its hydrogenation and dehydrogenation temperatures are currently too high, about 200C versus 80C required for transportation applications. The long term goal of this project is to develop high hydrogen storage capacity materials via doping Li2NH by anions. The PI hypothesizes that anions doping can be used to tune structures and properties of ionic compounds (Li2NH and LiNH2), which are key factors controlling hydrogen storage reactions. The PI bases his hypothesis on the observations that 1) anion/cation interactions dramatically affect catalyst performance, reaction kinetics, and reaction selectivity, 2) anion can selectively modify the properties of solid materials, 3) different Cl= containing promoters exhibit the same promoting effect on the dehydrogenation of LiNH2/LiH, which is clearly an indication of anion effects, and 4) Li2NH with O= ion showed much better hydrogen storage performance than that without O= ion. The specific aims of this experimental work are to: 1) correlate the effects of doping-anions on the hydrogen storage reactions of Li2NH with their intrinsic properties; 2) evaluate how anions doping affects the structures and properties of Li2NH and LiNH2; and 3) examine the effects of anions doping on the intermediate species of hydrogen storage reactions of Li2NH. This research has significant intellectual merit. Although metals and cations were widely used as promoters, anions have not yet been recognized as effective components to promote the hydrogen storage materials. Knowledge gained from this project on how anions doping affect the structures and properties of hydrogen storage materials could provide a new approach for developing new hydrogen storage materials. This project also has multiple broader impacts. The highly effective storage materials developed in this research can lead to low cost hydrogen storage materials which will impact the commercial feasibility of fuel cell vehicles, thus reducing the requirement of oil. This research has also strong impacts on the education of students. A "summer institute in hydrogen energy" program will be created. This program will promote the knowledge and skills of hydrogen energy science and engineering into the high school science classroom via training high school teachers. This project will train one graduate and one undergraduate student in this area. In addition, the PI is hoping to use this project to recruit under-represented (female) high school students as summer interns to his research group.