Design Of Co-based Catalysts And Their Application In Electrocatalytic Ammonia Synthesis

Ammonia（NH₃）,as one of the important industrial raw materials,huge demand for every year.At present,mainly through the Haber-Bosch on industrial method to produce ammonia on a large scale.The conditions for Haber-Bosch process need to consume large amounts of energy and emissions of greenhouse gases,cause great pollution to the environment.Under the current situation of fossil energy exhaustion and global greenhouse effect intensification,it is urgent to find a green and sustainable way of industrial nitrogen fixation and ammonia synthesis.Therefore,the electrochemical ammonia synthesis reaction at room temperature and pressure,as a mild nitrogen fixation reaction with low energy consumption and high utilization rate,has become a hot topic of current research.In order to realize the efficient electrochemical ammonia synthesis reaction,it is necessary to design and prepare efficient ammonia synthesis catalyst reasonably:accelerating the adsorption of N₂and activating to inhibit the competitive reaction HER,low reaction overpotential,and high NH₃selectivity,etc.In this paper,the research content is as follows:1.Through the adoption of synthesized by three steps demonstrated the modulation of surface properties of CoP by delicate preparation of O-CoP/CNT with hydrophobic surfaces and abundant O-moieties for high-performanceNRR.O-CoP/CNT reached a high NH₃yield of 39.58μg h^-1mg_c^-1_atand FE of 19.4%at-0.5 V in 0.1 M Na₂SO₄,superior to the benchmark NRR catalysts.Moreover,it also exhibited remarkable long-term stability with no obvious current density decay for 48 h electrolysis.Sufficient control and ¹⁵N isotope labeling experiments have unambiguously confirmed the N source of NH₃production.Furthermore,in-situ Raman spectroscopy detected reaction intermediates and identified the reaction pathway.DFT calculations revealed that the CNT coating can efficiently suppress HER due to its hydrophobic surface and more preferable N₂adsorption,and the O-moieties can also effectively decrease the barrier of the rate-determining step（N₂^*→N^*-N^*H）.This work may guide and inspire future modification and design of efficient NRR catalysts.2.Through the liquid phase method to synthetic Fe₁Co₁-LDH HNC with hollow nanocages and used as an excellent and economical electrocatalyst for electrochemical ammonia synthesis reduction under environmental conditions.The Fe₁Co₁-LDH HNC catalyst exhibits high selectivity and excellent activity for theNRR in a N₂-saturated Na₂SO₄electrolyte,achieving a high NH₃yield rate of 16.8μg h^-1mg_c^-1_atand a high FE of 14.7%at a lower overpotential.After 72 h long cycle test and cycle test 5 times,the attenuation of electric current density is not obvious,ammonia production rate and FE almost no change.And the catalyst before and after the reaction of XRD,TEM map do contrast,found material and has no obvious change,these can prove that the catalyst has better catalytic stability.¹⁵N isotope labeling experiment and strict control experiment,has been clear about the reaction product of NH₃ammonia source.Hollow nanocage lamellar structure provides a larger NRR reaction reaction area and the active site,through different dispensing proportion of Fe,Co elements to distinguish NRR catalytic material elements of the contribution to the problems in the process of reaction.The active sites of the reaction and the intermediate active products of theNRR reaction were determined by in-situ Raman spectroscopy.