| CO2 is one of the main gases causing the greenhouse effect;thus,electroreduction of CO2(CO2RR)can not only effectively alleviate the greenhouse effect,but also turn waste into various compounds with commercial application value,such as ethanol,ethylene,n-propanol(C2-C3 products)and CO.Therefore,studies should focus on the CO2RR to prepare C2-C3 compounds.However,the current research shows that most catalysts have significantly insufficient activity and stability for electrocatalytic reduction of CO2,and the selectivity needs to be improved.Therefore,the biggest challenge for electroreduction of CO2 is to design efficient catalysts with high activity,high stability,and high selectivityCopper-based catalysts have attracted wide attention because of their low cost and high selectivity for the formation of C2 products,especially Cu/Cu2O catalysts with a high selectivity for C2 products.In addition,the MOF has a regular structure,which is beneficial to obtain Cu/Cu2O particles with uniform size after reduction.Therefore,the main research work in this dissertation is to use a simple MOF derivation strategy to obtain MOF-derived catalysts and apply them to the electrocatalytic reduction of CO2.The specific experimental research is as followed:(1)Application of Cu/Cu2O@rGO derived from MOF-199@rGO composite material in electrocatalytic reduction of CO2The MOF-199@rGO material was prepared by hydrothermal synthesis and characterized by SEM,FT-IR and XRD.MOF-199@rGO as the precursor was electroreduced to obtain Cu/Cu2O@rGO material that then was characterized by SEM,TEM,FT-IR and XRD.The carbon paper coating Cu/Cu2O@rGO was used as the working electrode,and a platinum electrode was used as a counter electrode and a saturated calomel was used as a reference electrode to perform a potentiostatic electrolysis experiment.According to the analysis results,the reduction products were ethanol,ethylene and n-propanol.The effects of the types of materials and electrolysis potentials on the electrocatalytic reduction of CO2 were investigated On the Cu/Cu2O@rGO material at-1.9 V vs.RHE,a faradaic efficiency(FE)of 54%could be obtained.The current density for the C2-C3 products was 17.7 mA/cm2,which was 1.9 times higher than that on Cu/Cu2O material derived from MOF-199.At the same time,the current density for H2 is only 0.5 times than that on Cu/Cu2O materials,showing that the combination of rGO and Cu/Cu2O is beneficial to catalyse the formation of C2-C3 products and inhibit the hydrogen evolution reaction.However,the material can only stabilize electrolysis for 50 minutes and the catalytic stability needs to be improved.(2)Application of Cu/Cu2O@NG materials derived from MOF-199 and NG in electrocatalytic reduction of CO2The first system study found that although the Cu/Cu2O@rGO catalyst has a good electrocatalytic ability towards reduction of CO2,its catalytic stability needs to be improved.NG can not only serve as a carrier to disperse metal particles,inhibit their agglomeration,but enhance the activity of the catalyst.The pyridine N contained in NG can stabilize the metal particles,which is beneficial to increase the life of the catalyst.Therefore,MOF-199 and NG,as precursors,were electroreduced to obtain a new electrocatalyst with a high activity and high stability for efficient CO2RR into C2-C3 products in the second system.A series of Cu/Cu2O@NG materials derived from MOF-199 and NG were synthesized and named Cu/Cu2O@NG-1,Cu/Cu2O@NG-2,and Cu/Cu2O@NG-3,respectively.And they were characterized by SEM,TEM,EDX mapping,XPS and XRD.The effects of material types and electrolysis potentials on the electrocatalytic reduction of CO2 were discussed.The potentiostatic electrolysis data showed that Cu/Cu2O@NG-2 materials showed the best electrocatalytic performance,with the highest FE(56%)and corresponding current density(19.0 mA/cm2)for C2-C3 products at-1.9 V vs.RHE.And the catalytic stability of Cu/Cu2O@NG-2 material is remarkably enhanced,compared with that of Cu/Cu2O@rGO material. |
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