Hydrogen Production From Ammonia Decomposition Catalyzed By Plasma And Metal Nitride

As a clean and renewable energy,hydrogen has the advantages of high combustion value and no impact on the environment.It is a promising energy source that can replace fossil fuels.By organically combining hydrogen energy and fuel cell technology,the consumption of oil and natural gas in the transportation industry can be significantly reduced,thus greatly improving the level of energy security.However,the biggest bottleneck of hydrogen energy utilization is its safe storage and rapid release.From the perspective of hydrogen storage,ammonia is an ideal hydrogen storage material,which has high molecular hydrogen content and is easy to liquefy and transport;More importantly,ammonia decomposition to produce hydrogen is a process without carbon oxide emissions.So far,there is still a lack of research on low-cost ammonia decomposition to produce hydrogen.In this paper,dielectric barrier discharge plasma（DBD）is used to cooperate with metal nitride catalyst to achieve ammonia decomposition conversion rate of nearly 100%at low temperature.The specific results and conclusions are as follows:（1）Using cheap metal nitride catalysts（Mo₂N,W₂N,TaN,NbN）,the efficiency of ammonia decomposition to hydrogen production under pure plasma catalysis,traditional thermal catalysis and plasma synergy mode was investigated,and the emphasis was placed on the catalytic decomposition of ammonia to hydrogen production under atmospheric pressu re using DBD plasma synergy catalyst.Firstly,by comparing the catalytic activity of different metal nitride catalysts,it was found that the activity of Mo₂N catalyst was significantly higher than that of other three nitride catalysts.Secondly,when the plasma is coupled with the metal nitride catalyst,the efficiency of ammonia decomposition and hydrogen production will be greatly improved,which is significantly higher than that of the thermal decomposition of ammonia using only the catalyst and the decomposition of ammonia using pure plasma,and a significant positive synergistic effect of plasma catalysis is obtained.Using Mo₂N catalyst,the complete conversion of ammonia was realized under the conditions of NH3 feed rate of40 sccm,plasma input power of 26.4W and catalyst dosage of 0.8 g.At the same time,compared with thermal catalysis,the temperature of complete conversion of ammonia will be470℃from 510℃.（2）Based on the Mo₂N catalyst,the influence of the macro size of the catalyst on the DBD plasma discharge parameters was studied,and its influence on the hydrogen production efficiency of ammonia decomposition and the synergy between the plasma and the catalyst was further explored.Three kinds of Mo₂N catalysts with different particle sizes were prepared by pressing and sieving Mo₂N powder.It was found that the size of catalyst particles significantly affected the number and intensity of current pulses during DBD discharge.The large particle size,that is,the large discharge space,promotes the more effective conversion of electrical energy into chemical energy.Therefore,Mo₂N with large particle size shows stronger synergy than powder catalyst,further reducing the temperature of complete conversion of ammonia（<420℃）.This paper combines transition metal nitrides with low temperature DBD plasma technology,explores the activity of different catalysts used for plasma catalytic decomposition of ammonia to produce hydrogen,expounds the effect of catalyst particle size on ammonia decomposition,and indicates the possibility of further reducing the decomposition temperature and energy consumption of ammonia in the future.