Preparation Of Nano SnO_x And Bi Cathode And Its Electrocatalytic Reduction Of CO₂

In recent years,electrochemical reduction technology of carbon dioxide has been widely used.This phenomenon is caused by many reasons.For instance,it has mild and controllable reaction conditions.Moreover,the energy required for electro-reduction of carbon dioxide can be obtained from other renewable energy sources such as solar energy and wind energy.For this technology,formic acid,methanol,methane,ethane and other valuable products can be produced.Among them,formic acid,as an important industrial raw material,is widely used in pesticides,leather,pharmaceuticals and other industries.Furthermore,formic acid can be directly used as fuel for fuel cells.However,there are still some shortcomings in this technology.For example,due to the poor activity and selectivity of the catalysts used in the electro-reduction of carbon dioxide,the short life of the catalysts limits the scale of the production of formic acid.Therefore,it is urgent to prepare micronano-structured catalysts with high activity,selectivity and stability.For this report,the specific content of it is as follows:?1?Nano-SnO_x catalysts were prepared by simple low-temperature hydrothermal method and used in the experiment of electro-reduction of carbon dioxide to produce formic acid.For this experiment,the change of surface morphology and structure of nano-SnOx catalyst under different reaction temperature and time was studied.Firstly,the morphology,crystal structure and valence state of elements were characterized by SEM,XRD and XPS.Then a working electrode?SnOx/GDE?was formed by coating the catalyst on the surface of GDE for carbon dioxide reduction experiments.Finally,the catalytic performance of SnOx/GDE electrode for electro-reduction of carbon dioxide was evaluated by CV,EIS and potentiostatic electrolysis experiments.The experimental results show that the catalyst SnO_x?75-10?has the best catalytic performance when the reaction temperature is 75?and the reaction time is 10 h.More specifically,under the condition of-1.8 V vs.SCE and the current density of the catalyst is 45.7mAcm^-2,the faraday efficiency of formic acid production reaches 93.5%.Apart from this,the electrolytic potential has a great influence on faraday efficiency of formic acid production as well.The faraday efficiency of formic acid production increases gradually when the electrolytic potential shifts from-1.5 V vs.SCE to-1.8 V vs.SCE.When the electrolytic potential is further negatively shifted to-1.9 V vs.SCE,the faraday efficiency is increased due to the enhancement of hydrogen evolution reaction.At the same time,the stability of SnO_x?75-10?/GDE was studied as well.The results show that the stability of the electrode is poor in the continuous electrolysis,which may be caused by the pollution of the electrode surface and the reduction of formic acid in the cathode.?2?Bi electrodes with different morphologies were prepared by simple electrochemical deposition under different parameters and used in the experiment of electro-reduction of carbon dioxide to produce formic acid.SEM results show that the electrodes prepared by different deposition methods have different morphologies and structures:Bi electrodes with pine needle structure,Bi electrodes with strip structure and Bi electrodes with regular hexagonal structure were prepared by pulse electro-deposition,constant current deposition and potentiostatic deposition respectively.Further,combined with the electrochemical results,the catalytic activity of the hexagonal Bi electrode is higher than that of the branched and rod Bi electrode.Specifically,under the condition of-1.8 V vs.SCE and the current density of Bi electrode with hexagonal structure is 19.15 mAcm^-2,the faraday efficiency of formic acid production can reach 100%,which can be attributed to the fact that Bi with regular hexagonal structure has more edge points than Bi electrodes with other morphologies.In addition,the slight attenuation of faraday efficiency and current density can be neglected due to the chemical stability of the catalyst over 24 h.In a few words,Bi electrode is expected to achieve the goal of low energy and high efficiency,which is more conducive to practical industrial applications.