Preparation And Electrocatalytic Performance Of Ni-based Nanomaterials For CO₂ Reduction

Electrochemical reduction of carbon dioxide（CO₂）into value-added chemicals（such as CO,CH₄,HCOOH,C₂H₄,etc.）is an effective strategy for achieving carbon neutrality because it can be performed under mild conditions such as room temperature and ambient pressure.However,due to the high stability of the C=O chemical bond of CO₂,the kinetic process of CO₂ reduction reaction（CO₂RR）is sluggish and overpotential is high.Noble metals,such as Au,Ag,and Pd,exhibit excellent performance in CO₂-to-CO conversion,but high cost and scarcity hinder their large-scale applications.Therefore,it is of great significance to develop high-performance,non-precious metal electrocatalysts for CO₂ reduction.In recent years,nickel-nitrogen-carbon（Ni-N-C）catalysts have been widely regarded as one of the most promising CO₂RR catalysts due to their high activity,simple preparation and good stability.Based on this,in this thesis,nickel-based porous carbon materials and nickel-based heterostructure carbon materials were designed and synthesized from nickel element,mainly by regulating their nanostructures and the coordination environment of active sites to inhibit the structural collapse during cycling or accelerate electron transfer ability,thereby improving cycling stability and optimizing electrochemical performance.The main research contents are as follows:First,Ni-based porous nitrogen-doped carbon Ni/N-C catalysts were designed and synthesized by confinement strategy and hard template method.It demonstrated a high selectivity in the electrocatalytic CO₂ reduction performance test,with a Faradaic efficiency of over 90%in the wide potential range from-0.65 to-0.90 V（vs.RHE）,and a maximum efficiency of 91.1%at-0.80 V.The partial current density of CO is about16.22 m A cm^-2.The catalyst also exhibits remarkable stability,retaining about 91%selectivity of the initial activity for 20 hours of continuous electrolysis at-0.8 V.After that,a porous carbon nanofiber catalyst with Ni/Ni₃ZnC_0.7 heterostructure was successfully prepared by electrospinning technology,and a high Faradaic efficiency of91.5%was obtained at-0.8 V,corresponding to a CO partial current density of 11 m A cm^-2.The CO selectivity remains at 93.4%after continuous electrolysis for 45 h,which was superior to the Ni-N-C and PNCF electrocatalysts without heterostructures.Density functional（DFT）theoretical calculations also confirmed that CO₂ molecules were more easily activated on the Ni/Ni₃ZnC_0.7 heterostructure,which is conducive to the generation of*COOH and CO,and improves the conversion efficiency of electrocatalytic CO₂.This work demonstrates that it is a feasible strategy to enhance the selectivity of electrocatalytic CO₂ reduction by rationally constructing heterostructures.