The Mechanism Of Ammonia Decomposition And Catalyst Desing On The Surface Of Nickel Monolayer Supported On Tungsten Carbide

NH₃ is a hydrogen-rich poisonous compound,it is very important to transform NH₃ into N₂ and H₂ to reduce the environmental pollution,it will bring a severe influence on environment and provide green energy for human.As the cleanest and ideal energy,hydrogen energy can also be gotten.Therefore,catalytic decomposition of NH₃ is an effective way to remove NH₃ and gets new energy.In the catalytic decomposition of NH₃,there are two points,one is the design of the catalyst and the other is specific process of decomposition mechanism.The electronic structure calculcations were performed by employing periodic density functional theory,using NH₃ decomposition on Ni/WC?0001?surface,we calculated the adsorption energy,activation energy,reaction heat and geometry parameters,we detailed analysis the decomposition mechanism of NH₃.?1?Different transition metals of atomic monolayer supported on tungsten carbide have been system studied.The adsorption energy,geometric structure and electronic structure of the different transition metals in the adsorption sites were calculated.The research shows that the most stable site of different transition metals supported on tungsten carbide of termination with tungsten surface are hcp sites,the adsorption energy of Ni atomic adsorb on the tungsten carbide is the largest,the bond length between the Ni atomic and the surface atomic among the metal is the shortest,the d state of Ni atomic is most close to the Fermi level,and tungsten carbide supported on Ni monolayer has the highest chemical activity.?2?The adsorption and decomposition of NH₃ on the Ni/WC?0001?termination with tungsten were system studied.The geometry and electronic structure of adsorption about the different related species on the surface were calculated.The results were compared with Ni?111?and Ni/Pt?111?.The calculate results of d centroid show that,the d centroid of Ni/WC?0001?-W surface is more close to the Fermi level,and it has higher catalytic activity.NH₃ on the different surfaces by its lone pair electrons orbit adsorb on the top sites priority.We detailed calculated the mechanism of NH₃,the result shows that NH₃ dehydrogenation decomposition step by step is main decomposition way,N+N?N₂ reaction is the rate-determining step,the other reaction path of NH₃ decomposition on the termination with tungsten surface is moredifficut,because of the higher activation energy of priority form N-N bond.?3?The adsorption and decomposition of NH₃ on the Ni/WC?0001?-C surface,the different related species on the surface of the adsorption sites and adsorption energy were calculated.The most stable sites of NH₃ and NH₂ are the hcp and bridge sites,respectively.The most stable adsoption sites of NH₃,NH₂,NH,N and H are top,bridge,fcc,hcp and fcc sites respectively,the N₂ is desorption surface.NH?N+H is the rate-limitting step,and the NH is the rich product.The other reaction paths with the N-N bond formed first,then stepwise dehydrogenation is relatively difficult due to the high activation energy barrier.