Study On Nanoporous FeNbMoP Alloy And Its Electrochemical Nitrogen Fixation Performance

Ammonia（NH₃）is an indispensable chemical product for production and life,and a new type of energy storage material.Conventional industrial ammonia synthesis using the Haber–Bosch process requires temperatures of 400-500°C and pressures of 10-30 MPa,and is accompanied by the production of CO₂ gas.In recent years,ammonia synthesis by electrocatalytic nitrogen reduction（e NRR）under mild conditions has received a lot of attention.In electrocatalytic nitrogen reduction,nitrogen combines with protons in water to form ammonia,avoiding harsh conditions and allowing easy control of the reaction without producing harmful gases.However,electrochemical nitrogen reduction reactions also suffer from slow reaction kinetics and poor selectivity,and the development of efficient and stable electrocatalysts is the key to solving these problems.Fe Mo-based catalysts have good stability and selectivity,and have good potential for application in electrocatalytic nitrogen reduction.In this paper,nanoporous FeNbMoP catalysts were prepared using a dealloying method,their surfaces were modified and their electrocatalytic nitrogen reduction performance was investigated.The main findings are as follows:（1）Non-precious metal nanoporous FeNbMoP alloy catalysts with self-supporting structures were prepared by electrochemical de-alloying and applied to the catalysis of electrochemical nitrogen reduction reactions.The nanoporous structure has a large specific surface area and provides a medium and electron transfer channel.the addition of Nb elements facilitates the formation of phosphide in the alloy,and the appropriate amount of Nb atoms can promote the transfer of electrons in Mo atoms,which effectively modulates the electronic structure of Mo,Fe and P,enhances N₂ adsorption and improves the ENRR performance.The self-supported nanoporous np-Nb-5 catalyst exhibited good ENRR catalytic performance,obtaining a relatively high ammonia yield of 23.3μg h^-1cm^-2 at a potential of-0.57 V in a 0.1M PB electrolyte,while showing good long-term service stability.（2）The nanoporous FeNbMoP catalyst was modified with noctadecyl-thiol to form a hydrophobic layer on its surface.At a potential of-0.7 V vs.RHE,sample C18@np-Nb-0showed improved ammonia yield and Faraday efficiency compared to the catalyst without hydrophobic layer modification,while sample C18@np-Nb-5 containing Nb showed a decrease in ammonia yield.The presence of Nb elements in the alloy promotes the formation of Mo-P bonds in the catalyst,and after modification with noctadecyl-thiol,the thiol bonds interact with the Mo-P bonds and competing hydrogen precipitation reactions（HER）dominate the process,thereby inhibiting the nitrogen reduction reaction.The hydrophobic layer improved sample C18@np-Nb-5 exhibited excellent selectivity and good stability.