Study On Preparation Of Transition Metal Single Atom Catalysts And Its Hydrogen Production And Pollutant Degradation Performance

Single atom catalysts exhibit 100%theoretical atomic efficiency,high catalytic performance,and highly selective catalytic processes due to lack of metal-metal bonds,unique electronic structure of unsaturated coordination,and clear coordination environment,respectively.And it is widely used for energy conversion and pollution control.However,there are key scientific problems such as low metal loading,poor single-atom uniformity,unclear regulation of single atoms on active species and weak synergistic effect between diatoms.To solve the above-mentioned problems,we have conducted relevant research as follows:1)A synthetic strategy of ligand-assisted supramolecular self-assembly has been developed.Its main mechanism functions include:under the complexation between organic ligands and metal ions,regulating the content of each metal in the supramolecular precursor;using hydrogen bonds to increase the melting point,which can avoid the agglomeration of metal atoms at high temperatures;pyrolyzing precursor under an inert atmosphere to fix the metal aiom on g-C₃N₄（CN）.This strategy can not only universally prepare high-loading single atom catalysts M₁/CN（M=Cr,Mn,Fe,Co,Ni,Cu,Zn,Ag,and Cd）,but also can prepare double single-atom catalysts and hectograms level single-atom catalysts.2)A loading mass of 10.0 wt%and new uniform coordination configuration Ag-N₂C₂/CN was synthesized by citric acid chelating silver nitrate assisted supramolecular strategy.The Ag atomic dispersion and Ag-N₂C₂ configuration have been identified by material characterization.Experiments and DFT calculation further confirm that Ag-N₂C₂ can expand the light absorption range,regulates the electronic structure,reduces the H₂ barrier,and promotes the effective separation of photogenerated electrons and holes.As a result,the Ag-N₂C₂/CN shows much better H₂ evolution activity and good cycle stability under 60 hours of visible light irradiation than that of the same content of Pt _NP/CN.3)A loading mass of 7.0 wt%and Fe-N₄ configuration Fe₁/CN was prepared by oxalic acid chelating iron nitrate-assisted supramolecular strategy.Performance test experiments show that Fe₁/CN efficiently activates PMS and rapidly degrades 4-CP,and its removal rate is 5.4 times that of the equivalent Fe _NP/CN.Both the active species test and the trapping agent experiment confirm that the Fe₁/CN activated PMS has a selectivity of 100%to generate ¹O₂.And the rate of formation of ¹O₂ can be effectively controlled by the size of Fe and the exposure rate of Fe atoms.Electrochemical tests and DFT analysis confirm that the highly uniform Fe single atom induces the oxidation of PMS to generate ¹O₂.In addition,Fe₁/CN shows strong anti-anion,cation,natural organic matter interference ability,wide p H tolerance,and good cycle stability.4)Fe₁Zn₁/CN with Fe and Zn diatoms loaded on CN was prepared by the supramolecular strategy assisted by ligand co-chelation.Activity experiments show that Fe₁Zn₁/CN possesses a synergistic effect between diatomic sites,which can efficiently activate PMS to produce active species such as O₂^·-,¹O₂,and Fe（IV）.The degradation rate of DCP is 0.95 min^-1,which is 2.8 and 188.6 times of Fe₁/CN and Zn₁/CN,respectively.Fe₁Zn₁/CN has a good mineralization effect on DCP degradation,and its mineralization rate can reach 70%.In addition,Fe₁Zn₁/CN also has strong anti-anion,cation,and natural organic matter interference ability,and wide p H tolerance.