| The construction of carbon dioxide/carbon monoxide electroreduction reaction(CO2RR/CORR)catalysts with different structures is helpful to uncover the relationship between material structure and CO2RR/CORR performance,and to provide more ideas for the CO2RR/CORR catalyst design in the future.From this point of view,this thesis focuses on the structural design or the structural regulation and induction effects during electroreduction-of oxide precursors-to enhance the CO2RR/CORR activity of the catalysts deriving from them.By applying the synchrotron radiation X-ray absorption spectroscopy(XAS),the dynamic changes of the catalyst structure under CO2RR/CORR conditions were observed.Combined with density functional theory(DFT)theoretical calculations,the catalytic mechanisms were also analyzed.The find-ings of this thesis are as follows:1.The mesoporous Cu catalyst deriving from mesoporous Cu2O achieves efficient and stable electroreduction from CO2 to C2+products with 83%of Faradaic efficiency.The experimental results from the compact Cu control and in-situ synchrotron XAS tests have demonstrated that the residual oxide(Cu~+)in compact Cu is not the key active site for C2+production,and the mesoporous Cu catalyst is the copper phase but con-taining trace oxidation state meanwhile.DFT calculations show that subsurface oxygen(Osub)is likely to be the origin of excellent C2+activity obtained on m P-Cu.2.A new method that adjusting the structure of Cu2O catalysts via using iodide ions is proposed,and 78%of Faradaic efficiency from CO2 to C2+products was achieved on this catalyst.With the adsorption of iodide ions on Cu2O and Cu,the re-duction rate of Cu2O was accelerated,and the Cu was induced to reconstruct into a porous structure.The fitting results of synchrotron XAS test show that the porous Cu catalyst exhibits a coordination number(CN)of 7.7,which is located in the CN range of 6-8 that favors the CO=CO coupling reaction.This explains the excellent C2+cata-lytic activity of porous Cu well.3.In the flow cell,the strong adsorption interaction between CO and Cu2O was applied to accelerate the reduction rate of Cu2O.During this process,Cu adparticle would be induced in-situ along with the formation of the pure Cu catalyst,on which 23%of Faradaic efficiency from CO to n-propanol could be achieved.Comparing with the catalytic performance of three controls,the adparticle catalyst has the best catalytic ac-tivity for electroreduction CO towards n-propanol.The CO partial pressure experiments indicated that the adparticle contains active sites that are capable of enhancing CO ad-sorption,densifying CO concentration,as well as stabilizing C2 intermediates.In line with the DFT theoretical prediction,the low coordination sites on the adparticle can promote the formation of n-propanol by enhancing the binding strength of CO and C2intermediates,while reducing the reaction activation barriers of CO=CO coupling and CO=C2 coupling.4.Nano-Sn O2 catalysts were obtained by anodizing,laser ablation and reflux heat-ing.The Sn O2 catalyst obtained by anodizing exhibits a porous structure,which greatly improves the Faradaic efficiency from CO2 to formic acid of 30%comparing with that of the original Sn foil.Compared with anodizing catalyst,the Sn O2 catalysts obtained by laser ablation or reflux heating are smaller.The CO2RR tests show that the laser ablation catalyst has good potential in selectively producing formic acid from CO2RR,and the preparation process of the catalyst needs further optimization. |
