Study On The Electrochemical Reduction Of Carbon Dioxide By Tin-Based Electrodes

The increase of CO₂concentration in the atmosphere leads to the greenhouse effect,which greatly affects the ecological balance of climate and nature.Therefore,the conversion of CO₂ into renewable fuels through clean and eco-chemical processes has become a matter of great concern to scientists.CO₂ electrochemical reduction reaction products can be easily controlled by potential,temperature,and electrolyte concentration.Therefore,electrochemical reduction of CO₂is an important method ro convert CO₂ to useful chemicals..Among different electrocatalysts,tin-based electrocatalysts have been proved to have high activit、high selectivity、high stability and be low-cost electrocatalysis for the electroreduction of CO₂.Its main product is formic acid,which is an important intermediate in the pharmaceutical and chemical industries.In this paper,a tin-based composite electrode material was prepared as a catalyst for the electroreduction of carbon dioxide by hydrothermal method and electrodeposition.The main contents are as follows:1.A SnS₂ precursor was deposited on the carbon felt by hydrothermal method and then calcined in an air atmosphere to grow porous Sn O₂.The prepared Sn O₂ inherits the Sn S₂ precursor and forms a mesoporous structure during the air calcination process,which enlarges the contact surface area between the electrode and the electrolyte.The porous layered nature of Sn O₂ in combination with conductive carbon felt as three-dimensional support and current collector promote charge and mass transfers during the electrochemical reaction.This provided more active centers for the reaction.The faradaic efficiency of formic acid synthesis reached a maximum of 62.4%at-1.6 V（vs.3M Ag/Ag Cl）,and the current density reached 25 m A·cm^-2.2.Sn_xCo_y/CC materials with different molar ratios of Sn and Co wwere prepared by electrochemical deposition on carbon cloth（CC）.The results show that when the content of Co in the bimetal is 40%,the carbon cloth is wrapped by rice spike-shaped cubic bimetal particles,and the electrolytic faradaic efficiency of formic acid production can reach as high as 57.4%at-1.8 V（vs.3M Ag/Ag Cl）,which is far higher than the faradaic efficiency of formic acid production with single metal Sn on CC.This result shows that the proper amount of Co doping can effectively improve the electrocatalytic performance of single metal Sn.3.Sn-Co composites with different molar ratios were electrodeposited on a highly-conductive copper foam substrate with a large specific surface area.The electrochemical reduction of CO₂ into formate was then studied with these composite electrodes.Results have shown that with copper foam coated with 95%Sn and 5%cobalt at a potential of-2 V（vs.3M Ag/Ag Cl）,the faradaic efficiency of formic acid synthesis from CO₂ was 72.2%.This was much higher than the 51%observed with copper foam coated with Sn only confirming the good CO₂ to formate reduction performance of Sn-Co composites.