Construction And Catalytic Properties Of Ruthenium Based Catalysts Electrochemical Reduction Of Nitrogen

Environment is the material basis for human survival and development.However,the ecological damage caused by environmental pollution and the energy crisis caused by over exploitation of coal and oil have seriously threatened the sustainable demand of human production and development.Therefore,scholars all over the world think that the development of green and clean new energy technology is of great significance to the sustainable development of human beings.Ammonia?NH₃?is one of the highest annual output?about 1.5million tons?industrial products in the world.It is mainly produced by the traditional Haber Bosch process with high temperature and pressure.The annual consumption of this process exceeds 1%of the global total energy supply.At the same time,the CO₂ produced by the process burning fossil energy exceeds 300 million tons,accounting for 1.6%of the global total CO₂ emissions.Therefore,it is of great economic and environmental value to integrate renewable energy and realize the electrochemical conversion of N₂ to NH₃ by electrocatalytic reduction.However,the electrocatalytic synthesis of ammonia is faced with the problems of high activation energy barrier of N₂ and strong competition of hydrogen evolution reaction,which results in low ammonia production rate of the catalytic system.Therefore,it is an important task to design and construct high active and selective catalysts for the electrochemical synthesis of ammonia.In the electrochemical synthesis of ammonia catalyst,ruthenium?Ru?based nanocrystalline catalyst has attracted extensive attention due to its strong ability to activate N₂.However,at present,the activity of Ru based nanocrystalline catalysts is still relatively low,and the NH₃ production rate is lower than 50?g/cm^-2·h^-1.In order to improve the catalytic performance of Ru based metal catalyst,we introduce defects in crystal structure and heteroatom doping,regulate its atomic structure and electronic structure,improve the activation of Ru based metal catalyst on N₂,and realize the construction of high activity and high selectivity catalyst for electrochemical synthesis of ammonia.The experimental results of this paper include the following two aspects:?1?For Ru nanoparticles,through simple surfactant coating and rapid annealing,the"connection"between the nanocrystals was realized.The experimental results show that there are a large number of grain boundaries and stacking faults in the connection area between Ru nanocrystals,which makes the performance of the catalyst significantly improved compared with the original Ru nanoparticles.Under the over potential of-0.1 V vs.RHE,the Faraday efficiency?FE?of the"linked"Ru based nanocrystalline catalyst is up to 7%,and the ammonia production is up to 29.305?g/cm^-2·h^-1.The mechanism study shows that the defects in the"linked"Ru based nanocrystalline catalyst are not only the highly active electrocatalytic sites,but also the reduction of the overall work function,which is conducive to the chemical adsorption and electron transfer of N₂ on the catalyst and promotes the catalytic reaction of ammonia synthesis.?2?The effect of heteroatom doping on the catalytic performance of Ru based metal catalysts was systematically investigated,and the Co-Ru bimetallic catalysts with excellent performance were selected.By introducing 10%Co doping,the Co-Ru catalyst can produce8.13%Fe and 120?g/cm^-2·h^-1 ammonia under the over potential of-0.1V vs.RHE.At the same time,we studied the electron transfer phenomenon in CO Ru bimetallic catalyst,and explored the possible mechanism of high activity ammonia synthesis performance of Co-Ru catalyst from the perspective of electronic structure.In this paper,a set of control methods to improve the electrochemical synthesis of ammonia with Ru based metal catalyst is provided from the point of view of single substance modification and alloying.The results provide a new idea for the design of catalyst for the electrochemical synthesis of ammonia.