Preparation Of Single Atom Co/Graphene Catalytic Cathode And Degradation Of 2,4-dichlorobenzoic Acid

Chlorinated organic compounds are widely used as intermediates and solvents in chemical synthesis pharmaceutical and pesticide.They are highly toxic and difficult to degrade in water.Other treatments of chlorinated organic pollutants have the disadvantages of complete degradation and complex process.The electrocatalytic process has the advantages of simple,efficient and complete degradation.At present,most researches on catalysts focus on precious metal nanoparticles,which have the problems of low metal utilization and low selectivity.With a special electronic structure,single atom catalysts have high specific surface activity,and the utilization efficiency of metal atoms.This subject intends to develop a heteroatom-doped porous carbon material supports a single atom Co-dispersed catalytic cathode which can be used in hydrodechlorination and oxygen reduction reaction to take full advantage of the electrochemical reduction-oxidation stepwise reaction.The 2,4-dichlorobenzoic acid?2,4-DCBA?was used as target pollutants to explore the electrocatalytic performance and degradation mechanism.First,the metal precursor?Co Zn-ZIF?was generated by the combination of metal and organic ligands.The graphene,Co Zn-ZIF and S-containing ligand 2,5-thiophene dicarboxylic acid were effectively assembled by the hydrothermal reduction method,and the metal single atom catalyst was obtained by thermal reduction.The single cobalt atom anchored on sulfide graphene?Co-SG?cathode catalyst is further optimized for the three additive ratios,metal loading,and pyrolysis temperature.The metal of 1%Co-SG was dispersed,and other heteroatoms were also dispersed uniformly on the surface of graphene.The central atom Co coordinated with the nitrogen?Co-N?and oxygen?Co-O?atoms to form a new structure.S was mainly doped in the carbon structure of graphene in the form of-C-SO_x-.The contents of N and S were 2.3 and 1.6 wt.%,respectively.The doping of metal and heteroatoms increased the degree of defects and the formation of active sites.Electrochemical performance tests proved that 1%Co-SG can generate atomic H^*significantly higher than 2%and 3%Co-SG catalysts at 0.35 V?vs.RHE?with good metal dispersibility,achieving electrocatalytic hydrodechlorination?EHDC?of 2,4-DCBA,which proves that Co,N,and S co-doped materials have the ability to adsorb and generate atomic hydrogen.Under oxygen saturated conditions,the oxygen reduction reaction?ORR?current density of 1%Co-SG can reach 4.51 m A·cm^-2 at 0.5?0.6 V?vs.RHE?.The mass activity of 1%Co-SG was 1.65 A·mg_Co^-1.The 1%Co-SG can provide 90%H₂O₂selectivity during 0.40?0.70 V?vs.RHE?.1%Co-SG catalyst had higher catalytic activity under both in EHDC and ORR.The Co SAC-SG cathode was prepared from 1%Co-SG single atom catalyst to investigate the degradation mechanism of 2,4-DCBA.When the current density reached 50 m A·cm^-2,the initial solution p H was 5,the electrolyte Na₂SO₄ concentration was 0.05 mol·L^-1,and the initial concentration of 2,4-DCBA was 20 mg·L^-1,2,4-DCBA has the removal rate 90.8%and 92.4%in cathodic compartment and anodic compartment,.respectively.Under the optimal process conditions,the removal efficiency of TOC is more than 80%,the dechlorination rate is 83.7%.The degradation of 2,4-DCBA was relatively stable after 5 cycles.Through the determination of intermediate products and active substances during the degradation of 2,4-DCBA,it was determined that the 2,4-DCBA dechlorination process follows 2,4-DCBA?o-chlorobenzoic acid?benzoic acid.The dechlorination product was further decomposed into small molecule organic acids,and finally degraded by the hydroxyl radicals generated during the indirect oxidation reaction process.