Preparation Of Mo-containing Materials And Their Research On Activation Of Nitrogen Electrocatalytic Reduction

The production of ammonia plays a significant role globally,with approximately 80%of it being used in the production of agricultural fertilizers,while the rest serves as fundamental raw materials for pharmaceutical and industrial production.Moreover,ammonia has the potential to act as a carbon-free energy carrier and intermediate storage medium,rendering it a promising application prospect in future energy industries.The successful development of synthetic ammonia industry not only alleviates the agricultural production pressure brought about by population growth but also promotes the development of related industries,altering the global energy structure.Currently,industrial ammonia production mainly relies on the demanding Haber-Bosch process.This method not only consumes vast amounts of fossil energy but also releases significant amounts of greenhouse gases.Therefore,exploring an energy-saving,efficient,and environmentally friendly ammonia production route is urgently needed to mitigate these issues.Compared with the traditional Haber-Bosch process,electrochemical nitrogen reduction reaction（NRR）is recognized as a sustainable and green ammonia production method.However,the bottleneck in the current research on NRR lies mainly in the difficulty of N₂ adsorption and activation,leading to slow reaction kinetics and low Faradaic efficiency（FE）caused by competing hydrogen evolution reaction（HER）.Therefore,finding efficient and stable catalysts to accelerate NRR kinetics and suppress HER has become a hot research topic.In this study,a combination of experiments and density functional theory（DFT）calculations was used to systematically investigate the modification of molybdenum-containing materials and strategies for improving the efficiency of electrocatalytic ammonia synthesis.The research results obtained are as follows:Firstly,a simple and low-cost method was employed to synthesize Fe₂O₃nanoparticles derived from MOF,which were uniformly dispersed on MoSe₂ to form a bifunctional anchoring structure（Fe₂O₃/MoSe₂）.The Fe₂O₃/MoSe₂composite exhibited excellent nitrogen fixation activity,with a maximum NH₃production rate of 46.25μg·h^-1·mg^-1 at-0.5 V vs.RHE potential and the highest FE of 9.6%at-0.6 V vs.RHE potential.Additionally,the Fe₂O₃/MoSe₂composite showed good stability and durability in recycling tests.Density functional theory（DFT）calculations showed that the interface charge transfer from Fe₂O₃ to MoSe₂ could enhance the conductivity of the Fe₂O₃/MoSe₂material.Furthermore,compared with single materials（Fe₂O₃ and MoSe₂）,the free energy barrier for the ammonia synthesis-determining step（*N₂ to*N₂H）was lower for the Fe₂O₃/MoSe₂ composite,significantly improving its electrochemical nitrogen reduction reaction（NRR）activity,which was consistent with experimental results.This work provides a promising avenue for green synthesis of NH₃.Secondly,the study successfully synthesized Mo₂C catalytic materials doped with different Fe contents using hydrothermal and calcination methods.Electrochemical experiments showed that 5%Fe-doped Mo₂C achieved the highest NH₃ productivity of 36.6μg·h^-1·mg^-1 and a high Faradaic efficiency of10.3%at-0.3 V vs.RHE potential,which was much better than the original Mo₂C material and most reported NRR catalysts.In addition,density functional theory（DFT）calculations demonstrated that 5%Fe-doped Mo₂C could activate N₂ molecules better than original Mo₂C and 11.1%Fe-doped Mo₂C due to its lower energy barrier（0.84 e V）.This study provides an attractive non-precious metal catalyst for efficient electrocatalytic N₂ fixation.Finally,MoSe₂ nanodots were assembled on multilayered Ti₃C₂ MXene through a simple one-step hydrothermal method to obtain a highly efficient and stable NRR catalyst（MoSe₂/Ti₃C₂ composite）.The MoSe₂/Ti₃C₂ composite exhibited excellent NRR activity,with a maximum NH3 production rate of60.87μg·h^-1·mg^-1 at-0.55 V vs.RHE potential and the highest FE of 9.3%at-0.25 V vs.RHE potential,far superior to that of individual MoSe₂ or Ti₃C₂MXene components.Additionally,the MoSe₂/Ti₃C₂ composite showed outstanding stability and durability in cycling tests,demonstrating enormous industrial potential.Theoretical calculations showed that the excellent NRR catalytic activity of the MoSe₂/Ti₃C₂ composite was mainly attributed to the high conductivity of the multilayered Ti₃C₂ nanosheets,which not only promoted electron transfer but also addressed the aggregation issue on the surface of MoSe₂ nanodots.