Interface Regulation Of Cu₂O Catalyst And Its Electrocatalysis Of CO₂ Study On Reduction Reaction Mechanism

Carbon dioxide(CO2)can convert into high value-added carbon-based fuel showing great application significance for meeting "double carbon" goals.Among several feasible strategies for CO2 reduction,electrochemical CO2 reduction reaction(ECO2 RR)is regarded as the most attractive CO2 conversion technology due to its advantages such as mild conditions and effective utilization of waste electric energy.In this system,the copper-based catalyst is the only cathode material that can reduce CO2 to hydrocarbons and oxygenates,whereas copper’s poor stability,low product selectivity,and high overpotential hinder the generation of multi-carbon products.In addition,the structure and composition of the Cu-base oxide catalyst(Cuδ+)are in a dynamic evolution process during the CO2 RR process,which also greatly affects its catalytic activity and selectivity.At present,the primary problem of this class of catalysts is that it is easy to be reduced in the process of CO2 reduction,which weakens its catalytic performance.Therefore,the development of copper-based oxide catalysts with high stability,high activity,and low overpotential is the key to achieving efficient CO2 reduction to produce highvalue-added chemicals.This paper focuses on Cu2O,the catalytic performance of Cu2O was optimized utilizing morphology regulation,Schottky junction/heterojunction construction,and the electrocatalytic CO2 reduction process.The relationship between the morphology,crystal-facet,grain boundary,heterojunctions/Schottky junction structure of Cu2O base catalyst,and product selectivity was studied in detail.The main research contents of this paper are as follows:1)An ultra-thin two-dimensional(2D)Pd@Cu2O electrocatalyst with a controlled interface size of Schottky junction has been prepared by a simple ultrasound-assisted assembly method.The material can generate a controllable and tunable Syngas product across a wide potential range(-0.37～-0.87 V vs.RHE),wherein,the Faraday Efficiency(FE)of syngas is higher than 80%.Electrochemical tests revealed that the ultra-thin two-dimensional structure has a large specific surface area,which facilitates the rapid transfer of electrons from the Cu2O bulk phase to the Pd surface,thus improving the surface charge distribution of the Schottky junction catalyst,accelerating the activation of CO2 and stabilizing Cu2O.Density functional theory(DFT)calculation revealed that the surface of Cu2O is conducive to the adsorption of*COOH intermediates.In addition,*COOH is easy to combine with the active H on the adjacent Palladium hydride(PdH)surface to form CO,and the competitive hydrogen evolution reaction(HER)was significantly inhibited.The catalyst structure in this work constructed reduced the risk of rapid deactivation of Pd due to CO poisoning to a certain extent,as well as slowing down the transition of Cu+ to Cu0 in the CO2 RR process,providing a preliminary experimental and theoretical basis for other similar studies.2)Cu2O twin crystal cubes(Tc-Cu2O)and octahedrons(To-Cu2O)with multigrain boundaries were successfully prepared by a one-pot method,and a Cu2O@Cu2S heterojunction catalyst was synthesized by anion exchange strategy.The heterojunction catalyst can produce ethanol(C2H5OH)at a low potential.C2H5OH selectivity was found to be highly dependent on the facet of Cu2O,with TcCu2O@Cu2S outperforming To-Cu2O@Cu2S.Detailed electrochemical experiments and density functional theory(DFT)calculations reveal that this heterojunction with interface coherent structure and suitable band structure can facilitate electron transfer from Cu2O to Cu2S,leading to long-term stability(>24 h)of Cu+,the introduction of Cu2S increases the CO coverage rate,a high concentration of CO tends to spill over toward the grain boundaries,where ethanol is produced by*CHOH_*CO coupling.This work provides a new idea to precisely design C2+production catalysts by regulating the interface configuration.3)The electrocatalyst with the size of 35±5.5 nm Ag/Cu2O was prepared by the solvothermal coreduction method.By regulating the molar ratio of Ag and Cu,the optimal load of Ag can be modified on Cu2O exposed on specific crystal facets for efficient conversion of electrochemical CO2 RR to C2 product The results of the test in the H-type electrolytic cell show that the FE(C2H4+C2H5OH)of Ag/Cu2O2 catalyst at-0.95 V vs.RHE is about 47.1%,which is 3 times of Cu2O.In addition,the introduction of co-catalyst Ag increased the reactive sites and improved the surface charge distribution of the catalyst,which played a role in stabilizing the active species Cu+.This work provides a feasible strategy for a Cu2O-based catalyst to promote the electrochemical production of C2 from CO2 RR through noble metal catalyst modification.