Theoretical Study On The Application Of Carbon-based Two-Dimensional Materials In Nitrogen Cycling Reactions

Nitrogen（N₂）is a very abundant resource that can be converted into ammonia（NH₃）for the manufacture of fertilizers.At present,the Haber-Bosch method is still the main way to synthesize ammonia in industry,but the obvious shortcomings of this process make the synthesis of NH₃ still a great challenge.In addition,in order to alleviate the problems caused by energy shortage,it is very important to develop clean energy such as hydrogen energy.The main way to obtain hydrogen energy is water splitting,but the shortcomings are also very obvious.Therefore,it is very necessary to develop other alternative ways to obtain hydrogen energy from water splitting.The possible by-product hydrazine（N₂H₄）in the NRR process can be catalytically oxidized to N₂ and H₂,which may be a good way to replace the traditional water splitting to obtain hydrogen energy.This process is undoubtedly very important for the recycling of N elements.In this paper,we have investigated the possibility of doping different levels of B atoms onto N-modified graphene as N₂ reduction electrocatalysts and the potential of transition metal monoatomic loading onto monolayer C₂N materials for N₂H₄ oxidation electrocatalysis.the results are shown below:（1）We improved the catalytic activity for NRR by doping B atoms into FeN₄/G material to change its electronic properties.In particular,the computational results show that Fe-B₂N₂/G is the most promising catalyst for NRR reduction with a required confinement potential of-0.65 V.Interestingly,the introduction of B atoms can effectively modulate the interaction between the central Fe atom and the N₂H^*intermediate,thereby enhancing the catalytic activity of NRR.It is worth noting that the competing HER can also be well inhibited during the reduction process,ensuring efficient selectivity.（2）We designed a series of transition metal single atoms supported on C₂N monolayer（TM@C₂N）as electrocatalysts for the oxidation of hydrazine（N₂H₄）.The calculated results show that these TM@C₂N have high stability,which can be attributed to the strong interaction between metal atoms and N atoms in the C₂N monolayer.More importantly,according to the calculated Gibbs free energy curves,Ru@C₂N,Mo@C₂N,Ti@C₂N,Co@C₂N,and Fe@C₂N all exhibit high Hz OR catalytic activity.Especially Ru@C₂N exhibits the most excellent catalytic activity with the lowest confinement potential of-0.24 V,which can be attributed to its special electronic properties.