Fabrication Of Ag And Sn Based Nanostructured Electrocatalysts For Electrochemical Carbon Dioxide Reduction

Carbon dioxide(CO₂)is considered to be one of the most important greenhouse gases.The concentration of CO₂ in the atmosphere has been increasing year by year,which has become a serious environmental and climate problem.Electrochemical CO₂reduction(CO₂RR)to carbon-based fuels is a promising strategy for renewable energy storage and net carbon emission.However,CO₂RR technology still faces the following problems that need to be solved urgently:1)the high reaction potential caused by the high stability of CO₂ molecules;2)low yield due to catalyst mass transfer problems;3)the CO₂RR reaction path is complicated,which results in poor product selectivity;4)traditional noble metal catalysts have high cost and poor stability.High-performance catalysts are usually obtained by adding grain boundaries,constructing ultra-thin structures,synthesizing small-sized particles,and constructing unique nano-porous structures.In this regard,the the CO₂RR of ultra-fine Ag nanowires and nano-porous Sn-based electrocatalysts were studied in this paper,and the specific morphology and structure of the catalyst were characterized and analyzed in detail.The specific research contents are as follows:(1)Mass production of silver nanowires(Ag NWs)with ultrathin diameter(?35 nm)and a high aspect ratio(>1000)wrer prepared from an optimized polyol solution and the interaction between nanowires formed a large area electrode with pore structure.The Ag NWs electrode displayed good activity to convert carbon dioxide(CO₂)to carbon monoxide(CO)in high Faradic Efficiency(FE)of?80%under low working potential(-0.9 V vs.RHE),at the same time the fraction of CO/H₂ can be tuned from1/1 to 4/1 by changing the reduction voltage(-0.8?-1.3 V vs.RHE).During the 12 h stability test,the current density and CO Faraday efficiency were stable.(2)We prepared Sn O₂ aerogels(Sn O₂-AO_x)using an anodization approach under different voltage.The as-prepared Sn O₂-AO₁₀ aerogels exhibit a tubular structure(poresize:?45 nm)with abundant nanograins within the size range of 3?5 nm.The porous structure provides a large specific surface area(90.1 m² g^-1)and high porosity(0.74 cm³ g^-1),while the grain boundaries render a strong CO₂ affinity.When tested as the electrocatalyst for the CO₂RR,the aerogels maintain 95%Faradaic efficiency(FE)towards CO₂RR and 73%FE for HCOOH at-0.8 V vs RHE for 12 h.Miscellaneous characterizations combined with theoretical calculations were employed to elucidate the correlations between the structure and composition of the aerogels and their CO₂RR performance.(3)Using glucose(C₆H₁₂O₆)and stannous chloride dihydrate(Sn Cl₂·2H₂O)as raw materials for ball milling and carbonization treatment,Sn-Sn O₂/C₈₀₀ was prepared at low cost and on a large scale,and its simulated flue gas in CO₂RR was studied(Adjust the mixture N₂/CO₂ content ratio).Test the electroreduction reaction of the catalyst at-0.8 V vs.RHE potential under 100%,90%,80%,50%,25%,15%CO₂ content,and the results show that CO₂ achieves complete conversion when the CO₂ content is 15%.It is indicated that the introduction of N₂in the system promotes the electroless reduction of CO₂,and its deep mechanism remains to be further studied.