Study On Photothermal Catalytic Ammonia Synthesis Over Iron Based Metallic Materials

Ammonia plays an important strategic role in national production and is also one of the important chemical raw materials.Currently,the mainstream industrial synthetic ammonia（Haber Bosch process）requires high temperature（around 400℃）and high pressure（250 atmospheres）,and can cause a large amount of energy waste and environmental pollution.In today’s increasingly stressful energy environment,the negative impact of the traditional Haber Bosch process has clearly overwhelmed the planet.It is urgent to solve the environmental pollution and energy pressure caused by this process.Photocatalytic ammonia synthesis technology is considered as a new green catalytic method,which can significantly reduce energy consumption and environmental pollution.However,there are also shortcomings such as low light energy utilization rate and far lower ammonia production efficiency than the Hubble process.Therefore,the photothermal method of converging solar light to drive reactions is currently receiving great attention.It can effectively solve the problem of low utilization of infrared light by photocatalysis.At the same time,photothermal is also a clean energy source,which can solve the problem of high energy consumption compared to pure thermal catalysis.However,due to the BEP relationship in ammonia synthesis reactions,the development of high-performance catalyst materials for ammonia synthesis at low temperatures has been limited.Therefore,this article mainly conducts research in two directions:（1）Based on the method of photothermal catalytic synthesis of ammonia,breaking the BEP relationship in iron based catalyst ammonia synthesis through photoinduced electron transfer effects;（2）Introduce other transition metals to further modify iron based materials.And study the mechanism of its photothermal synergistic effect.The main research contents and conclusions are as follows:1.we reported an approach of bending the“seesaw effect”thus breaking the scaling relations over aα-Fe particulate metallic material（α-Fe-PR）,realizing highly efficient sustainable photo-driven thermal catalytic ammonia synthesis.The expanded high-index-facets exposed onα-Fe-PR could promote the dinitrogen dissociation,and a photo-induced electron transfer further accelerates the hydrogenation process,which breaks the inhibition of scaling relations in ammonia synthesis.For the first time,these reverse associated two steps were accelerated simultaneously over identical sites and ammonia production rate overα-Fe-PR reached 736μmol·g^-1·h^-1 at a low temperature of 350°C under atmospheric pressure with irradiation,showing a 30 times enhancement than in dark,which is even 112 times of the commercial fused-iron catalyst with promoters under the same temperature.This work designs a sustainable efficient system for ammonia synthesis and provides a new approach for breaking the scaling relations in heterogeneous catalysis.2.A Co-Fe bimetallic catalyst was designed and synthesized,with an ammonia production efficiency of 6200μmol·g^-1·h^-1under conditions of full spectrum driven photoheating at 500℃without additional heat sources.It is also revealed that the introduction of Co can increase the number of active sites in iron based materials without changing the position of active sites.Moreover,illumination can also promote the activation of nitrogen on the surface of Co-Fe bimetallic catalysts,which,combined with their multiple active sites,achieves 2.44 times the ammonia production performance of pure iron at the same temperature.The performance mechanism of this material fully unleashes the potential of photoheating as a clean energy technology,providing a good start for solar catalytic synthesis of ammonia.