Study On The Preparation Of N,P Co-Doped Carbon Material For Electrochemical Reduction Nitrogen

Ammonia?NH₃?is one of the most common industrial chemicals produced in today's economy,which not only exhibits a strong foothold in agricultural,plastic,and textile industries,but renders a stable hydrogen carrier.The reduction of N₂ to NH₃ is a kinetically complex and energetically challenging multistep reactions due to the chemical inertness of N₂ and limited by the thermodynamics.The electrocatalytic reduction approach is regarded as environmentally-benign process for NH₃ production,since they can be powered by a renewable electricity source and performed at room temperature and atmospheric pressure.Compared with the traditional harber-bosch method,the electrocatalytic reduction approach has low energy consumption with mild condition.However,one of the challenges associated with achieving artificial scalable conversion of N₂ to NH₃ under mild condition is how to develop highly chemical active and selective yet low-cost electrocatalyst to activate N₂.The synthesis of N,P co-doped carbon materials and the fundamental research of their electrocatalytic activity for N₂,selective and reaction mechanism were investigated.The porous structure and the heteroatom modification can be tuned by adjusting the synthetic process of carbon materials.The structure and composition of carbon materials were characterized by nitrogen adsorption,SEM,TEM,Raman spectrum,XPS and so on,cyclic voltammetry,linear sweep voltammetry,chronoamperometric curves were used to test the electrochemical properties of the carbon materials.The products of electroreduction reaction were characterized by UV-Vis spectrophotometer,gas chromatography,¹H NMR spectra and LC-MS.Furthermore,the electrocatalytic NRR mechanism on the NPC was characterized by electrochemical in-situ Fourier transform infrared spectroscopy that follows associative pathway.This paper mainly includes the following aspects:In chapter 2,we synthesis the N,P co-doped hierarchically structured nanocarbon?NPC?foam by pyrolysis of polyaniline?PANi?aerogels in the presence of phytic acid,can electrochemically convert N₂ into NH₃ in an acidic aqueous solution at room temperature and atmospheric pressure.The Faradaic efficiency and yield of NH₃produced on the NPC electrode in 0.1 M HCl solution are as high as 4.2%and 0.97?g h^-1 mg^-1 catalyst,respectively.The performance is resulting from sufficient catalytic active sites in carbon network and strong adsorption capacity toward N₂,hierarchical pore architecture covering from mesopore to macropore structure of NPC by BET,which can accelerate mass diffusion and promote electron exchange efficiency.The doping of N,P heteroatoms increased the active sites electrocatalytic properties of the carbon materials.More importantly,the mechanism of NRR process on N,P co-doped carbons has been unambiguously demonstrated that follows associative pathway by electrochemical in-situ FTIR.In chapter 3,the Fe anchored on substrate of N,P co-doped hierarchically structured nanocarbon?NPC?as electrode material Fe-NPC has been synthesized,which was used to study the effect of Fe on the electrocatalytic nitrogen reduction activity at room temperature and atmospheric pressure.The hierarchical pore architecture covering from mesopore to macropore structure was similar to NPC,which can accelerate mass diffusion and promote electron exchange efficiency.The doping of N,P heteroatoms especially Fe increased the active sites electrocatalytic properties and electrical properties of the carbon materials.The Faradaic efficiency and yield of NH₃ produced on the NPC electrode in 0.1 M NaOH solution are as high as 5.3%and 4.36?g h^-1 mg^-1 catalyst,respectively.Finally,the adsorption and evolution of nitrogen of NRR process on Fe-NPC has been demonstrated that follows associative pathway by electrochemical in-situ FTIR.In chapter 4,the N,P co-doped porous carbon?NP-C-MOF-5?with rich in mesopores was prepared from the coordination polymer of MOF-5 can serve as metal-free electrocatalyst for nitrogen reduction reaction?NRR?in HCl aqueous solution under ambient temperature and pressure conditions.The yield of production of NH₃ and N₂H₄·H₂O on NP-C-MOF-5 at-0.1 V vs.RHE is 1.08?g h^-1 mg^-1_cat.and5.77×10^-4?g h^-1 mg^-1_cat.,respectively.Moreover,the electrocatalytic NRR mechanism on NP-C-MOF-5 was investigated by electrochemical in-situ Fourier transform infrared spectroscopy?in-situ FTIR?,which provides theoretical and experimental support for design novel efficient NRR electrocatalyst in the future.