Design And Construction Of CuNi Bimetallic Carbon-based Catalyst And Study On CO₂ Electrochemical Reduction

CO₂ electrochemical reduction（CO₂RR）is a sustainable approach to chemical fixation of CO₂ and storage of renewable energy,which is expected to provide an achievable pathway to zero carbon cycling.However,there are thermodynamic and kinetic barriers to the reduction of CO₂ molecules,which can be solved under the method of electrocatalysis,thermal catalysis,photocatalysis,etc.,and supplemented by high-performance catalysts.Among them,electrocatalysis has attracted much attention because it can be carried out at room temperature and pressure,and can be powered by renewable energy sources.The research of high activity,high selectivity and nice stability is a crucial part of the realization of CO₂ electrochemical reduction.In this paper,a series of CuNi bimetallic nitrogen-carbon catalysts were prepared by ball milling and calcination method with copper phthalocyanine and nickel phthalocyanine as raw materials.The effects of ball milling conditions,carbon carrier types,Cu/Ni content and ratio on the properties of these catalysts were investigated.In addition,the catalyst was applied in a self-made zero-gap membrane electrode reactor to achieve amplification of current density and product selectivity,which will facilitate the industrial application of CO₂RR.The main research results are summarized as follows:（1）CuNi-N-C catalysts was constructed by using Vulcan XC-72R as carbon carrier to support CuPc and NiPc,and the influence of ball milling time on its catalytic activity was investigated.CuNi nanoparticles are surrounded by nanoscale Vulcan XC-72R to prevent excesssive aggregation.The addition of Vulcan XC-72R significantly improves the material’s electrical conductivity,and its bond with CuNi nanoparticles provides pathways for electron transfer.The high energy shear force generated by ball milling can imrove the interface state of the catalyst and conductive to expose more active sites.However,too long milling time has unfavorable effect on CO₂ reduction.In the range of 0～90 min,the catalyst obtained by ball milling for 30 min showed the most excellent selectivity of CO（73.8%）.Furthermore,because the CuNi-N-C catalysts only have two types of product（CO and H₂）,it can be performed as a catalyst to produce syngas,and the CO/H₂ ratio can be effectively regulated by controling the electrolytic potential.（2）Based on the study of Vulcan XC-72R as carbon substrate,the performance of the catalysts with no carbon substrate,C₃N₄ carbon substrate,C₃N₄ and Vulcan XC-72R double carbon substrate were explored respectively.C₃N₄ has a two-dimensional plane structure,which can be utilized as a self-sacrificing template at high temperature to provide structural guidance for the formation of catalyst.And C₃N₄ has the ability to introduce pyridine nitrogen and pyrrole nitrogen,which is conducive to enhance the adsorption of CO₂ and improve the reduction performance.The introduction of double carbon carrier can effectively integrate the characteristics of them,which can provide more anchoring sites for metal phthalocyanine,and accelerate the electron transfer between the carrier and metal nanoparticles.The CuNi-CN@V catalyst supported by C₃N₄ and Vulcan XC-72R presented an optimal faraday efficiency of78%at-0.67 V_RHE potential,which was superior to the materials of single C₃N₄ or Vulcan XC-72R carbon carrier.（3）CuNi-CN@V catalyst as a CO-producing catalyst,its product selectivity and electrolysis stability at high potential need to be further improved.On this basis,the CuNi-NC/NG series catalysts were prepared with GO and C₃N₄ as carbon substrate,and the effects of Cu/Ni content and ratio on the catalytic performance were investigated.GO has unique two-dimensional layered structure with abundant oxygen-containing groups and in-plane lattice defects,which have been confirmed to play a positive role in reduction reaction.The macrocyclic metal phthalocyanine can be anchored to GO in the form ofπ-πinteraction,which prevents the metal agglomeration during the calcination process,and the size of metal nanoparticles has indeed been significantly reduced.Comparing with single Cu/Ni catalyst,Cu₃₀Ni₃₀-NC/NG catalyst exhibited satisfactory selectivity,which possesses a faraday efficiency of 85.2%at-0.72 V_RHE,and showed good stability at high potential.The synergistic effect of Cu and Ni and the active sites of nickel oxide/copper nanocluster endow the catalyst excellent performance towards CO₂ electroreduction.When applied it to a zero-gap membrane electrode reactor,the CO selectivity is over 90%in a wide potential range.Besides,in the condition of FE_CO>80%,the current density can reach more than 9times than in H-type cell.This work provides a feasible method for the optimization of CO₂electrocatalyst and electrolyzer.