Study On Electrocatalytic Ozone Production Performance Of Boron And Nitrogen Co-Doped Mesoporous Carbon

Ozone as a commonly used oxidant,has been widely used in water treatment,industry,food and medical industries.Corona discharge method is mainly used to generate ozone all over the world.In order to overcome the shortcomings of this method,in recent years,scientific researchers have been committed to research electrolytic method to produce ozone.?-Pb O₂ is commonly used for electrolysis which has certain toxicity.It has been reported that boron-doped diamond?BDD?has excellent performance of electrochemical ozone production?EOP?,but diamond is expensive and cannot be used in industry.Based on this,the goal of this work is to find cheap carbon materials to replace diamond.There are too many carbon materials to be screened experimentally,so this paper used density functional theory?DFT?to analyze adsorption energy of the important reactive species?H₂O,O₂,and O₃?in the process of electrochemical ozone production.Catalysts with high adsorption energy for H₂O and O₂ are favorable for the decomposition of H₂O molecules and O₂ adsorption for further synthesis of O₃ and with low adsorption energy for O₃ are beneficial for the diffusion of O₃ and reduce the decomposition of O₃ are most likely to have excellent EOP performance.The calculation results exhibit that the multifunction-sites,pyrrolic-N,B co-doped defective mesoporous carbon material with a high content of pyrrolic N?D-BNC?for H₂O,O₂,and O₃ has adsorption energies of-1.2 e V,-1.7 e V,and-2.0 e V,respectively.It meets the above requirements for the adsorption energy of reactive species and has the potential of EOP.According to the guidance of theoretical prediction,D-BNC and a series of other heteroatom-doped carbon materials were successfully synthesized.It is proved by TEM,BET,and EPR that the surface of D-BNC is rich in mesoporous structures and defects;XPS and elemental analysis indicate that B and N were successfully doped in D-BNC;and the concentrations of dissolved and gaseous ozone were measured.The concentration of dissolved ozone for D-BNC was 3.54 mg L^-1 at 3.0 V vs.RHE,and the concentration of gaseous ozone for D-BNC was about 600 ppb at 25.00 m A cm^-1for 40 min.The results exhibit that the EOP performance of D-BNC is the best among all the comparison catalysts,and the experimental results are consistent with the theoretical predictions.In order to explain why D-BNC performs well,DFT calculation is used to further study the reaction mechanism of the EOP process.The calculation results show that the key in the EOP process is the formation of O₂ and O₃.Two^*O intermediates,which are located on the top site of the B atom and on a bridge site of the C and pyrrolic-N atoms have a sufficient potential to form an adsorbed^*O₂ molecule.During the last step of the O₃ formation,the B and its neighboring C atoms provide an adsorption site for^*O₂ and^*O respectively,forming O₃ molecules.In addition,defects play different roles in different EOP stages.The high activity of D-BNC can be attributed to synergetic effect played by pyrrolic-N,B,its neighboring C elements,and the defects.Furthermore,the five-membered cyclic structure formed among the B and the neighboring C atoms and that connects to O₃ reduces the activation energy?0.41 e V?of the compound and promotes the EOP.This work offers a new reference for the development of inexpensive metal free carbon-based electrocatalysts for EOP.