Design And Preparation Of Cu₂O Catalytic Material And Investigation Of Their Performance For Electrocatalytic CO₂ Reduction

Electrocatalytic CO2 reduction reaction(CO2RR),which use clean electric energy generated by renewable solar energy and wind energy to drive CO2 to be converted into fuel or high value-added chemicals at normal temperature and pressure,is a key technology to realize artificial carbon cycle and effectively mitigate the greenhouse effect and energy crisis.At present,Copper base material can effectively catalyze the conversion of carbon dioxide into C1 or poly-carbon reduction products.However,copper catalysts still face many problems,such as inevitable competitive hydrogen evolution reaction,complex reaction mechanism,diversification of products,low selectivity of target products and so on.Therefore,it is necessary to develop efficient electrocatalysts.In this paper,we designed and synthesized Cu2O nanomaterials with the aim of synthesizing low-cost and high-performance CO2RR catalysts,and systematically explored the electrocatalytic performance of such catalysts in the CO2RR process.The main research contents of this paper are as follows:(1)Study on the crystal surface controlled synthesis of Cu2O and its performance for electrocatalytic reduction of C02 to ethyleneThree kinds of Cu2O nanocrystals of different crystals were synthesized by simple wet chemical reduction method by regulating the surfactant vinylpyrrolidone(PVP).By means of XRD,SEM and TEM,it was confirmed that cubic Cu2O nanoparticles(o-Cu2O)mainly exposed(100)crystal face.octahedral Cu2O nanoparticles(o-Cu2O NPs)mainly exposed the(111)crystal face and truncated-octahedral Cu2O NPs(t-Cu2O-r100/111=0.36 or t-Cu2O-r100/111=1.73)exposed the(100)and(111)crystal faces.And the electrochemical CO2 reduction performance of different Cu2O NPs in CO2 saturated 0.1 M KHCO3 electrolyte was studied,these results shown that the t-Cu2O-r100/111=1.73 catalyst exhibited a Faradic efficiency of ethylene(FEC2H4)of 33.63%at-1.28 V(vs.RHE).Meanwhile,the performance of t-Cu2O catalysts with(100)and(111)crystal plane was better than c-Cu2O and o-Cu2O catalysts.The possible reason was that the synergistic effect between(100)and(111)crystal planes can promote the C-C coupling and facilitate the desorption of the product C2H4.This study provide a new way to enhance the electrocatalytic performance of Cu-based catalysts for CO2 reduction through crystal surface regulation.(2)Al-doped octahedral Cu2O as an efficient electrocatalyst to CO2 reduction for production of ethylene.In this paper,Al-doped octahedral Cu2O(Al-Cu2O)catalyst was synthesized by a simple wet chemical method.The selectivity of CO2RR products was improved by doping Al onto the surface of octahedral Cu2O by regulating the Al content.The AI-Cu2O was used as an efficient electrocatalyst for CO2RR with selective ethylene production.The Al-Cu2O exhibited a high Faradic efficiency(FEC2H4)of 44.9%at-1.23 V(vs.RHE)in CO2 saturated 0.1 M KHCO3 electrolyte.Al doping could induce charge transfer from the Al atom to the Cu atom,thus modulating the electronic structure of Al-Cu2O.The DFT calculation shows that Al-Cu2O catalyst can effectively reduce adsorption energy of the*CHCOH intermediate and promote the mass transfer of charges,thereby improving the CO2RR with high FEc2H4.After A1 doping into Cu2O,the center of d orbitals shift positively,which makes the d-band closer to the Fermi level.Furthermore,the density of electronic states increases,which was conceived to the interaction between Cu atoms and intermediates,thus facilitating electrochemical CO2 reduction process.This work proved that the metal doping strategy can effectively improve the catatlytic properties of Cu2O,thus provide a reliable method for CO2 cycling and green production of C2H4.(3)Study on the performance of sea cucumber Cu2O/Cu@N-C used in electrocatalytic reduction of CO2 to formateCu2O/Cu supported N doped C nanocatalyst(Cu2O/Cu@N-C)was prepared by a one-step solvothermal method using dimethylformamide(DMF)by controlling reaction time.The prepared Cu2O/Cu@N-C catalyst had a sea cucumber shape.Cu2O/Cu@N-C was mainly composed of C,Cu,O,N,and the valence state of Cu in the catalyst was 0 and+1.And the electrochemical CO2 reduction performance of three Cu2O/Cu@N-C-X catalysts in CO2-saturated KHCO3 electrolyte was studied.These results shown that Cu2O/Cu@N-C as an efficient electrocatalyst,selectively reduces CO2 to formate,and Cu2O/Cu@N-C catalyst exhibits a high FEformate of 89.26%at-0.98 V(vs.RHE)with a current density of 12.59 mA cm-2.In this study,Cu2O/Cu@N-C has a special morphology like sea cucumber,which can provide more active sites in the reaction process,enhance the adsorption and activation of CO2,and thus improve the selectivity of the catalyst to the product.