Preparation And Products Selectivity For CO₂ Electroreduction Of Oxide（Sn O₂,ZnO）Modified Cu-Based Electrode

The research on high-efficiency catalysts for electrocatalytic reduction of CO₂ is of great significance for solving environmental pollution problems and global energy problems.The copper-based electrocatalyst has the advantages of low cost and producing various products from CO₂ reduction,but the disadvantages of high hydrogen evolution and low selectivity of the target products is still challengable.In this study,porous Cu with large electrochemical surface area（ECSA）is used as the substrate,SnO₂ or Zn O is electrodeposited on the Cu substrate to inhibit the competition of hydrogen evolution reaction.Through annealing,the re-distribution of Sn and Cu atoms on the surface could be achieved,and then partially reduced oxides modified Cu electrodes with a high-density Cu-Sn interface are constructed by electroreduction.Higher selectivity for CO₂ reduction could be expected.Firstly,R-Cu/SnO₂ electrodes with different Sn contents were successfully prepared by electrodeposition-electroreduction using three-dimensional porous Cu foam as the substrate.The characterization results showed that the electrode surface was a honeycomb porous structure,and the main composition is partially reduced SnO_xand Cu.The introduction of SnO_x significantly inhibited the hydrogen evolution reaction,FE_H2 decreased from more than 70%to less than 40%.R-Cu/SnO₂ electrode shows the product selectivity law associated with the deposition time of SnO₂:FE_CO>FE_HCOOH when the deposition time of SnO₂ is less than 30 min,and FE_CO<FE_HCOOHwhen the deposition time is more than 45 min.RA-Cu/SnO₂ prepared by electrodeposition-annealing-electroreduction maintained a porous structure with a surface composition of Sn-SnO_x-Cu O_x-Cu.The characterization results showed that annealing promoted the redistribution of Cu/Sn atom on the electrode,and showed a lower metal valence after pre-reduction treatment.The performance of electroreduction of CO₂ showed that RA-Cu/SnO₂ with different SnO₂ deposition time has similar selectivity of reduction products.On the one hand,the ability to inhibit hydrogen evolution reaction was enhanced,and FE_H2 was about 20%.On the other hand,CO selectivity was significantly improved,FE_CO was higher than70%,only a small amount of HCOOH was formed,and FE_HCOOH was up to 6%.Cu/Zn NS and Cu/Zn NR were prepared by electrodeposition Zn O nanosheets and Zn O nanorods on porous Cu foam.The results show that the Zn O distribution on Cu/Zn NR surface is more uniform and the crystallinity is higher,and the CO₂ electroreduction performance is better than that of Cu/Zn NS electrode.Compared with Cu substrate,the CO₂ reduction selectivity is improved,and FE_H2 is suppressed to about 50%.