| With the rapid development of the social economy,the quality of life of the people has been significantly improved.However,while the economy is being developed,the protection of the environment has been neglected,which has caused great damage to the environment.Environmental pollution has become an urgent problem for all countries to develop environmental protection.Economic and effective pollutant treatment technologies are urgently needed.The continuous innovation of catalytic technology provides a new way to solve such environmental pollution problems.In recent years,because of isolated single iron atoms catalyst’ s advantages such as high activity,high stability,high selectivity and high metal atom utilization,it has been widely concerned in the field of traditional catalysis.However,in the field of environmental pollutant treatment,the research on the removal of pollutants by single-atom catalysts has just begun.The reaction mechanism and effect of pollutant removal are still unclear,and research work in this area is urgently needed.In view of this,this paper uses isolated single iron atoms as a model catalyst to preliminarily discuss the process of removing two typical pollutants.1 Synthesis and characterization of isolated single iron atoms catalyst:Isolated single iron atoms catalyst is mainly gained through the preparation of materials by hydrothermal method and high temperature calcination method.Characterization from XRD,TEM,SEM,XPS and HAADF-STEM showed that the catalyst has a dodecahedral shape and a unique atomic bonding state;at the same time,the iron atoms are uniformly dispersed on the carrer.2 Electrocatalytic removal of nitrobenzene(NB)by isolated single iron atoms catalyst:under neutral solution conditions,isolated single iron atoms catalyst can be used as electrode material to efficiently remove nitrobenzene and completely reduce it to aniline.The results of Tafel curve and impedance experiments show that the corrosion potential of the single-atom Fe electrode material is low,the electrochemical reaction resistance is small,and it is easy to transfer electrons to the reactant nitrobenzene.Meanwhile,the control experiment in heavy water and ESR test results show that in the electrochemical process,electrons(e-)can generate a large amount of hydrogen radicals with H3O+in a short time.We also analyzed the intermediates in the reduction process of nitrobenzene by high performance liquid chromatography.It is speculated that the mechanism of reduction and removal of nitrobenzene may be as follows:under the condition of electricity,the electrons in the circuit are rapidly transferred to the hydrated ion H3O+ in the solution which produces hydrogen radicals.Then,the hydrogen radical rapidly and highly selectively reduces nitrobenzene adsorbed on the surface of the working electrode to aniline.3 Catalytic removal of nitrogen oxides(NO)by isolated single iron atoms catalyst:the experimental results of visible light photocatalytie removal of nitrogen oxides confirmed that compared with nano-iron catalysts,the removal effect of single-atom Fe materials in the process of visible light photocatalytic removal of nitric oxide has been significantly improved.And the sample still maintains high catalytic activity and stability in the cycle experiment.In-situ injfrared and ion chromatography tests showed that the photocatalytic oxidation products of NO were mainly nitrate-based;the results of BET and NO/O2-TPD tests showed that isolated single iron atoms catalyst has stronger ability to adsorb NO than nano-Fe,which is beneficial to the photocatalytic oxidation reaction;the simultaneous capture experiments confirmed that the active species were electrons(e-)and superoxide anion radical(O2-):DRS and photocurrent tests showed that the Fe loading can effectively enhance the carbon and nitrogen compounds in visible light.The response of the zone greatly improves the separation efficiency of its photogenerated·carriers. |
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