4-Aminopyridine And Bimetallic Catalysts To Modify Carbon Electrodes For Electrocatalytic Reduction Of CO₂

The electrochemical reduction method is recognized as an extremely promising technology for carbon dioxide conversion and utilization,which can catalyze CO₂ into low-carbon fuels or high value-added chemical products.It is conducive to the emission reduction of greenhouse gases and the utilization of carbon resources.However,electrochemical reduction of CO₂ still suffers from many problems,such as low product selectivity and poor electrode catalytic stability.In addition,most of the previous studies have used homogeneous catalysis or noble metal catalysis,which would be not conducive to large-scale practical applications.Based on this,organic catalysts combined with non-noble metals were used to modify carbon-based electrodes for the purpose of building an efficient,stable and low-cost bifunctional electrode catalytic system,which can improve the performance of catalyzing CO₂ electroreduction to selectively form methanol by the synergic effect between different metals as well as the organic and the bimetallic catalysts.The crystal structure,microscopic morphology and element composition of the electrode catalysts were characterized using XRD,SEM,EDX,XPS.Meanwhile,the electrochemical performances of the electrode catalysts were further investigated by CV,LSV and i-t curve.The specific research work and conclusions of this paper are divided into the following two points:（1）4-aminopyridine with unique catalytic activity was immobilized on carbon paper electrode by electrochemical oxidation method,and non-noble metal Cu-Ni was further loaded on the electrode by electrochemical deposition.A series of C-Py-Cu-Ni composite heterogeneous electrode catalysts with different chemical composition were obtained by the deposition current density(20～50 m A cm^-2)of the electroplating solution.The experimental results show that the four electrode catalysts with different deposition current density have the ability to catalyze CO₂ reduction to alcohol,and methanol is the dominant.By comparing and characterizing the as-prepared electrodes,it was found that when the deposition current density was 40 m A cm^-2,the particles deposited on the surface of the C-Py-Cu-Ni-40electrode were smaller and uniform with higher coverage.In addition,C-Py-Cu-Ni-40electrode has more active sites and larger electrochemical active surface area.The catalytic activity of C-Py-Cu-Ni-40 electrode in the electrochemical CO₂ reduction was significantly better than that of the other three electrode catalysts under the same conditions.The Faraday efficiency of methanol production from CO₂ was up to 38%via nuclear magnetic resonance quantitative detection,without obvious attenuation in the 15 h electrolysis process,showing high catalytic stability.（2）A series of carbon supported electrode catalysts were prepared by incorporating nano metals（Sn,Zn,Sn-Zn）and organic catalysts（4-aminopyridine,Py）into the carbon-based electrode（pure carbon paper）via the same electrochemical oxidation method and electrodeposition method.It was found that the electrochemical active surface area of the C-Py-Sn-Zn electrode catalyst was superior to the C-Sn-Zn electrode,though they have similar micromorphology under the same electrodeposition conditions.Compared with the C-Sn,C-Zn and C-Sn-Zn electrode catalysts,the C-Py-Sn-Zn electrode has the best catalytic performance for the electrochemical reduction of CO₂,which could catalyze CO₂ to form methanol with Faraday efficiency of 59.9%at constant potential of-0.5 V vs.RHE.Moreover,it is worth mentioning that C-Py-Sn-Zn catalyst has a good stability,continuously electrolyzing over 26 h without loss of its activity.This may be due to the synergy effect of Sn-Zn bimetallic catalyst and Py organic catalyst,which would play an extremely important role in the electrocatalytic reduction of CO₂.