Fabrication Of Au And AuFe Based Materials And Their Performance Of Electrocatalytic Reduction Of Carbon Dioxide

The concentration of CO₂ in the air has rising sharply due to fossil fuels such as coal,petroleum and natural gas burning on an unprecedented scale,which causes a series of environmental problems threatening the subsistence of humanbeing.As for enclosure spaces like space shuttles and submarines,the concentration of CO₂ coming from breathing should be controlled under a specific value necessarily to ensure the survival of people in these places.It is a big chanllenge for human to convert CO₂ into value-added chemicals and then close the anthropogenic carbon cycle because of the rather stable structure of CO₂ molecular.Electrocatalytic CO₂ reduction using metal electrode is thought to be one of the most promising methods for CO₂ utilization considering its gentle reaction condition and easy operation.Herein,we fabricated C-Au and C-AuFe materials by Brust redution method and the one-pot nanoemulsion synthesis method.We carried out HRTEM,FTIR,XRD,XPS,XAFS,ICP-MS and ATR-IR to characterize the structure of Au-based materials and to explain the mechanism of CO₂ electroreduction.We used gas chromatography to characterize the gas products.We calculated Fafadaic efficiency?FE?and current density to evaluate the catalytic performance for the Aubased materials.We used cysteamine?CA?,2-mercapto-ethanol?ME?and 1-propanethiol?PT?as stabilizers in Brust reduction reaction and we got CA-capped C-Au,ME-capped CAu and PT-capped C-Au respectively by means of self-assembling of Au with sulfydryl?-SH?to form Au-S bond.The catalytic performances improve for three capped C-Au,compared with C-Au without ligand.The CA capped C-Au showed the best catalytic performance to electroreduce CO₂ at-0.9V?vs.Ag/AgCl?,with 95% FE for CO on-1.2V.The amount of CA can affect the morphology and catalytic performance of C-Au.The best molar ratio for HAu Cl4 and CA was 1:1.The ATR-IR showed that the “metal…NH2” structure in CA capped C-Au faciliates the formation of CO₂?-intermidiate,which improves the catalytic performance.Compared with Au foil,the current density of CA capped C-Au did not show dramatic decrease combining with 95% on FE for 10 h.We fabricated several C-AuFe materials with different Au:Fe ratios from 9:1 to 1:3.The C-AuFe with Au:Fe=3:1 performed the best ability to convert CO₂ into CO,better than its all counter parts with the ratios of 9:1,6:1,1:1 and 1:3.We also carried out self-assembling method to produce CA capped C-AuFe materials with different molar ration between AuFe nanoparticles and CA.The best ratio was 1:0.5,as the catalytic performance was better than no CA added.Especially,the CA capped C-AuFe with ratios of 1:1 and 1:3 showed decline in FE and CO current density,which meaned too much CA capping would close over surface area and do harm to catalysts.The carbon support would influence the catalytic activity improved by changing carbon black to multi-walled carbon nanotube?MWNT?which showed lower FE and CO current density,and carbon black with H2 S improved the catalytic activity.Noticeably,we found the Fe in C-AuFe was Fe oxide,and Fe would leach partly during CO₂ electroreduction and a core-shell like nanoparticle with Au shell and AuFe alloy core were presented.Characterizations also showed some vacancies in the coreshell structure nanoparticles,which were thought to contribute to the catalytic stability.90 hours CO₂ reduction reaction showed invisible decline in current density with the FE of 96%.C-AuFe material is a very stable and high-efficiency catalyst for CO₂ electroreduction.