Day: January 16, 2012

Li-N Compounds for Energy Applications

Thursday January 19, 2012 4:00-5:00 p.m.
ME-EM building, Room 112

Donggang Yao
School of Materials Science and Engineering at Georgia Institute of Technology

The critical issues of fossil fuels are their limited natural sources and contribution to the increase of atmospheric greenhouse gases. To solve those  problems, hydrogen is being developed as a promising alternative fuel, and the conversion of CO2 into valuable materials is considered as an effective approach to control the emission of greenhouse gases. In recent years, we have made an effort to develop hydrogen storage materials and to convert CO2 into novel solid materials.

Lithium nitride (Li3N), which is only one metal nitride that can be formed at room temperature, is an active material. This compound can be used to store hydrogen via its hydrogenation into lithium amide (LiNH2) and lithium hydride (LiH), which contain about 10wt% hydrogen.However, a potential issue regarding the N-based material for hydrogen storage is the generation of NH3, which consumes some H2 and also constitutes a poison for the downstream processes. The second issue is that the reversible hydrogen capacity of Li3N is about 5.5wt%, which isbelow 6.0wt% required for an effective on-board hydrogen-storage technique. This presentationwill demonstrate that the ultra-fast reaction between NH3 and LiH can eliminate NH3 during the hydrogen storage process of Li3N. Furthermore, it will show the reversible hydrogen capacity forLi3N can be remarkably enhanced by pre-doping LiNH2.

The conversion of CO2 represents a great challenge due to its high stability and low reactivity.Very recently, we explored lithium nitride for the CO2 conversion. It was demonstrated that Li3Ncan rapidly react with CO2 into two important types of solid materials carbon nitrides andlithium cyanamide. Different from current processes of CO2 conversion that are endothermic,this reaction is exothermic. Therefore, it constitutes not only a novel process for CO2sequestration, but also a unique approach for synthesis of carbon nitrides and lithium cyanamide.This presentation will discuss this novel process.