Synthesis Of Nanostructural High-Performance Cu-Pb Electrocatalysts For CO₂ Reduction

Electrocatalytic reduction of CO2 driven by renewable energy is a promising method to achieve CO2 balance and the storage of renewable energy.In the electrolysis process,some drawbacks still exist such as low current density and low energy efficiency caused by hydrogen evolution reaction(HER).The key is designing and preparing cheap and stable materials to depress HER,obtain good products selectivity and improve current density.Nanostructure and crystallinity of transition metals play an important role in catalyzing CO2 electroreduction.In this study,hierarchical nanostructures of heterogeneous Cu-Pb catalysts were prepared by a two-step electrodepositing-annealing-electroreduction(EAE)approach on 3-dimensional(3-D)commercial Ni foam.The prepared electrodes were characterized by various physical spectra to study its micromorphology and surface composition.The electrochemical characterizations of prepared electrodes were carried out by cyclic voltammetry,linear sweep voltammetry and double layer capacitance.CO2 electroreduction was tested on prepared electrodes and the products were analyzed.The electrolysis experiments include comparison between different electrodes on constant-potential,different potentials and stability test.The main research results are as follows:1.Cu nanowires(Cu NWs)of 200-400 nm diameter were built on the surface of commercial nickel foam substrates through an EAE step.Then,Pb nanoparticles with diameter of 5-10 nm were uniformly created on the surface of Cu NWs by a second EAE step.Bimetal Cu-Pb electrode with special nanostructure was prepared2.The nanostructural Cu-Pb electrodes catalyzed CO2ER at a current density of-9.35 mA cm-2(at-0.93 V vs.RHE)and The faradaic efficiency(FE)of the main electrolysis products CO and HCOOH is 50.6%?22.0%,respectively.The side product H2 was suppressed by 35.6%and CO and HCOOH were enhanced by 29.6%and 9.2%,respectively as compared to Cu NWs.The production of C2+liquid products such as CH3COOH,CH3CH2OH,CH3CH2CH2OH also improve.The prepared Cu-Pb electrodes show good CO2 electroreduction performance on the wide potential range of-0.23 V to-1.13 V vs.RHE.The selectivity of products and current density remain stable for a long time.3.The performance of Cu-Pb bimetallic electrode was optimized by changing the doping amount of Pb and the temperature of secondary heat treatment.The morphology,composition characterization results and the CO2 electroreduction performance of the prepared electrodes under different conditions were investigated.Moderate Pb doping can effectively inhibit the side reaction of hydrogen evolution and has little effect on total current density.Excessive Pb doping can lead to agglomeration of Pb grown on Cu nanowires and restrain the catalytic performance.The optimum preparation conditions are as follows:Pb electrodeposited of 30 C passing charge,second annealing treatment for 300?(close to melting point of Pb)in air atmosphere for 2 h.This work was aimed to develop an electrodeposition-annealing-electroreduction(EAE)approach for preparing hierarchical nanostructures of Cu-Pb bimetal electrocatalyst.The prepared Cu-Pb electrodes possess high performance toward CO2 electroreduction in terms of current density and controllable selectivity for H2,CO,and HCOOH.