The Preparation Of Mofs And Their Catalytic Performance For Ammonia Synthesis At Low Temperature And Atmospheric Pressure

To be one of the most important parts of chemical industry, ammonia synthesis is indispensable in national economy. However, the problem of low conversation rate per pass, the huge energy consumption and the discharge of greenhouse gas exist in conventional process of ammonia synthesis. Therefore, it has aroused great concern that the ammonia synthesis at low temperature and atmospheric pressure embrace the advantages of lower energy consumption, safety and environmental protection. In this case, superior performance and low-cost catalysts would play a crucial role in the low temperature and atmospheric pressure process of ammonia synthesis. MOFs are used as outstanding catalysts, which have merits of enormous specific surface area and their structure and properties easy to adjust.In this paper, Metal organic framework materials (MOFs) are synthesized by hydrothermal method to catalyze the reaction of ammonia synthesis. Our experiments synthesized four sorts of MOFs catalysts selecting three metal slat-Fe(NO3)3·9H2O, Co(CH3COO)2·4H2O and Cu(NO3)2·3H2O as precursors by using hydrothermal synthesis with 1,3,5-BTC, imidazole and BDC being electron-donating organic ligands. We used XRD, X-ray Photoelection Spectroscopy, N2 adsorption-desorption characterisations and FTIR to characterize the catalyst's composition and structure. Besides, the catalysts are applied to electrochemical ammonia synthesis to evaluate their electrochemical performance at ambient temperature. Finally, experimental results show that four kinds of catalyst coordinated successfully. The coordination bonds in MOF(Fe-BTC), MOF(Fe-BDC), MOF(Cu-BTC) and MOF(Co) are Fe-O, Cu-O and Co-N. These four catalysts have good catalysts's coordination bonds and crystal structure and perform good catalytic activities on electrochemical ammonia synthesis at ambient temperature, when MOF(Cu-BTC),MOF(Fe-BTC), MOF(Fe-BDC) and MOF(Co) as a catalyst are applied to the same experimental conditions of ammonic synthesis with N2 as the raw meterial, MOF(Fe-BTC) has the highest rate of ammonia synthesis up to 1.07236×10-9 mol×cm-1×s-1 at 80? and 1.0 V and its current efficiency is 4.11%. MOF(Cu-BTC) embraces the rate of ammonia synthesis up to 4.58×10-10 mol·cm-2·s-1 at 80? and 1.2 V and its current efficiency is 1.74%. MOF(Co) embraces the rate of ammonia synthesis up to 8.53×10-10 mo·lcm-2·s-1 at 80? and 1.2 V and its current efficiency is 2.23%. MOF(Fe-H2BDC) can reach the the rate of ammonia synthesis up to 6.763×10-10 mol·cm-2·s-1 at 80? and 1.2 V and its current efficiency is 1.51%, in which air is used as a raw material. Through these experiments, we not only realize adapting MOFs as catalyst in the electrochemistry, but also open up a new direction of MOFs catalysts on electrochemical synthesis of ammonia.