Systhesis Of Nano-tin Oxide Catalyst And Its Membrane Electrode For CO₂ Electrocatalytic Reduction

Electroreduction reaction of carbon dioxide?CO₂?can be conducted under normal temperature and pressure,at the meantime,the new clear energy can be applied to supply electronic energy in CO₂ electroreduciton process.Thus,conversion of CO₂ to the added-value liquid fuels and other liquid fuels and other useful chemicals via the electrochemical has a good prospect and research value.However,it still maintain the study stage and has some key issues need to be soloved.For example,the poor solubility of CO₂ in aqueous solution and the slow dynamics of the electrocatalytic reduction system,high overpotential and short lifetime of catatlyst.Therefore,it is urgent need to prepare a novel nano-catalyst,which has perfect catalytic performance,high electivity and good stability.In this work,a novel SnO_x nanostructured nanocatalysts was prepared by hydrothermal method.The composition and microstructure of the SnO_x catalyst were characterized by X-ray diffraction?XRD?,X-ray energy dispersive spectroscopy?XPS?,scanning electron microscopy?SEM?and transmission electron microscopy?TEM?.The electrochemical performance of SnO_x catalyst was studied by cyclic voltammetry?CV?and current-time?i-t?curves.In addition,a membrane electrode for the electrocatalytic reduction of CO₂ was prepared with the same method in a fuel cell,and tested its electrochemical performance.The effects of different preparation conditions,catalysts morphology,acid/alkaline membrane on selectivity and current efficiency of CO₂ reduction were discussed.In addition,the "three-in-one" membrane electrode for the electrocatalytic reduction of CO₂ was prepared by the method of fuel cell membrane electrode?MEA?,and the corresponding electrochemical performance was studied.The following results were obtained:?1?SnO_x nanocatalysts with different microstructure were synthesized by controlling the hydrothermal reaction conditions including temperature and time.The performance of CO₂ electroreduction show that the performance of SnO_x nanocatalysts with different microstructure have changed notely.SnO_x?120-12?nanotalyst?synthesised the reaction condition of 120 oC,12 hours?performs best,whose the onset potention of CO₂ can reach-0.565 V,and obtains the highest current density of-16.9 mA cm-2 at the potential value of-1.6 V.All of those performance has a close relationship with its loose microstruture.The electroreduction product anlysis result shows:the faradaic efficiency of SnO_x?120-12?nanocatlyst can reach37.3% with the potentiostat value of-1.5 V.?2?SEM and TEM results indicate that SnO_x?100-8?has a novel clear 3-dimensioned coralline-like structure,which is is comprised of the secondary structures which are made up of elongated triangular pyramid.However,with increasing to 12 hours,the coralline-like structure begins to collapse.Then the special morphology is collapsed completely and forms a flagstone-like structure made up with dense thick particles after 16 hours.XRD and XPS results indicate that SnO_x nanocatalyst is composited of SnO and SnO₂.XPS analysis shows that SnO surface is covered with a 1² nm thickness of SnO₂ layer.Furthermore,HR-TEM and XRD analysis show that SnO_x?100-8?is a nanocatalyst with polycrystalline structure,in which,the diffraction peak intensity of SnO?002?is obviously much higher than the diffraction peak intensity of the same lattice plane for SnO_x?100-16?and SnO_x?85-12?nanocatalysts.In addition,SnO_x?100-8?has the obviously stripe spacing of 0.240 nm,suggesting that lattice plane?002?plays a main role in improvement the performance during CO₂ electroreduction process.?3?Catalytic Reduction of Carbon Dioxide on SnO_x Catalysts by adding PVP during hydrothermal reaction.The results show that the catalytic reduction of CO₂ can not be improved by the doping of PVP.?4?The results show that the ions transported by acidic Nafion 117 membrane are H+.The alkaline anion exchange membrane Tokuyama A201 delivers OH-.For the production of formic acid process reaction:.In the presence of alkaline anion exchange membranes and KHCO₃ electrolyte,H+ in the cathodic compartment is mainly due to water electrolysis and hydrolysis of carbonic acid.The weak acid electrolyte inhibited its hydrolysis to a large extent,which is not conducive to the formation of formate.?5?A membrane electrode for the electrocatalytic reduction of CO₂ was prepared with the same method in a fuel cell.And the performance of CO₂ electrocatalysis was investigated by means of a similar fuel cell device.The SnO_x / GDL of the membrane electrode system can significantly reduce the diffusion resistance of the catalyst and increase the reaction concentration of CO₂ on the surface of the electrode,thus improving the current efficiency of the catalytic reaction,which provides a useful reference for the membrane electrode reactor applying the CO₂ electrochemical reduction technology.