Synthesis Of Palladium-based Material Their Application In Electrocatalytic N₂ Reduction Reaction

Since the discovery of the important role of ammonia(NH₃)in fertilizers,NH₃ has been regarded as a valuable compound.Its applications have expanded from the production of various chemicals,explosives,fibers,and plastics to pharmaceutical compounds,pulp and paper,refrigerators,green energy systems,and more.In order to meet the ever-increasing demands of society,the industrial synthesis of NH₃ can only be synthesized through the traditional Haber-Bosch process.This process needs to react nitrogen(N₂)and hydrogen(H₂)in a ratio of 1:3 under the severe conditions of high temperature of 350-550?and high pressure of 150-350 atm,but the NH₃ yield is less than 20%.Meanwhile,this process is accompanied by enormous amount of CO₂ release into environment.At the same time,the process is accompanied by the release of a large amount of CO₂,which is very unfriendly to the environment.Despite the presence of large amounts of N₂(78%)in the air,the process of converting N₂ to NH₃ is extremely difficult due to its inert nature,the strong thermodynamic limitations of N?N triple bond,and the lack of a permanent dipole moment.In recent years,electrochemical N₂reduction(NRR)can synthesize ammonia with the existence of electrocatalysts under ambient conditions,which has attracted great attention as an attractive technology due to the advantages of no CO₂ release and simple equipment.In recent years,the electrocatalytic nitrogen reduction reaction(NRR)has attracted great attention because of its ability to synthesize NH₃ through a catalyst under ambient conditions without releasing CO₂,and its simple equipment.This paper summarizes the research progress of strategies to improve the performance of NRR catalysts through literature research.On this basis,three high-efficiency Pd-based catalysts have been developed and their NRR performances have been studied.The specific content is as follows:1.Pd nanoparticles were modified by tannic acid(Pd-TA)for tunning its electronic structure,which can improves the dispersibility and stability of Pd nanoparticles.It is a mild and effective strategy to boost its nitrogen reduction reaction(NRR)activity.After synthesis,the catalyst was characterized and its NRR performance in sodium sulfate(Na₂SO₄)electrolyte was explored.The experimental results show that the NH₃ yield and Faraday efficiency(FE)of the Pd-TA catalyst are both high,which are 24.12?g h^-1mg^-1_cat.,9.49%,respectively,which is better than pure Pd nanoparticles and reported Pd-based catalysts and most other aqueous NRR electrocatalysts.2.Inspired by the fact that sulfur also plays an important role in the nitrogen-fixing of nitrogenase,we prepared palladium sulphide-reduced graphene composite(Pd S₂-r GO)by controlling the content of sulfur powder by high temperature solid-phase method.Experiments have found that S plays an important role in regulating the nitrogen reduction activity of Pd-based catalysts.In 0.1 M Na₂SO₄,the NH₃ yield of Pd S₂-r GO catalyst reached 22.52?g h^-1 mg^-1_cat.and a high faradaic efficiency of 7.06%at-0.50 V versus the reversible hydrogen electrode.At the same time,studies have also shown that it exhibits higher electrochemical stability,structural stability and higher stability.3.Among the transition metal oxides,Ti O₂ has the advantages of high thermal stability and non-toxicity,and is a highly adaptable semiconductor catalyst.It has been confirmed that it has strong photocatalytic nitrogen fixation performance.But its low conductivity greatly hinders its application in electrocatalysis.Studies have shown that Ti O₂ containing oxygen defects has good electrocatalytic activity for NRR.Our palladium-doped titanium dioxide(Pd-Ti O₂)nanoparticles prepared by the hydrothermal method are an efficient nitrogen reduction catalyst and have strong electrochemical stability,reaction activity and selectivity at ambient temperature and pressure.In 0.1 M Na₂SO₄,the NH₃ yield and FE of the Pd-Ti O₂ catalyst are 17.4?g h^-1mg^-1_cat.,12.7%,respectively.Compared with the NRR performance of the control material Ti O₂,Pd-Ti O₂ exhibits stronger NRR performance.The results show that Pd-doped Ti O₂ can greatly improve the NRR performance of the catalyst.