Electrocatalytic CO₂ Reduction To Syngas By Ag Loaded Carbon Aerogel And The Enhancement By Electrocatalytic Oxidation Of Ammonia In Anolyte

The burning of large amounts of fossil fuels has caused a shortage of resources.And excessive CO₂ emissions have also caused natural disasters such as global warming,melting of glaciers and acidification of seawater.The electrochemical conversion of CO₂ can fundamentally solve the problem of excessive CO₂ emissions and can also transform CO₂ to a variety of useful chemicals such as CO,CH₄,CH₃OH and so on.What's more,the resource shortage can be released to some extent.The types of electrocatalytic reduction products of CO₂ are complex such as CO,CH₄,CH₃OH and so on.If appropriate electrode materials were used to make the reduction products of CO₂ to synthesis gas composed of CO and H₂,the product can be directly used in Fischer-Tropsch reaction and it will be convenient for product collection.In this study,Ag loaded carbon aerogel was prepared as a catalytic material,and characterized by SEM,TEM,XRD and XPS.The reduction reaction of CO₂ was carried out at a constant potential.The yields of syngas composed of CO and H₂ and the corresponding Faradaic efficiencies under different conditions were investigated,and the effect of NH₃addition on the reduction of CO₂ was investigated at the first time.?1?The carbon aerogels were prepared by sol-gel method.The morphology and pore structure of the carbon aerogels were characterized by a series of characterizations so the basic physical characteristics of carbon aerogels were studied.The best R/C ratio of the carbon aerogel was selected to prepare catalysts.Three methods were attempted to prepare the Ag loaded carbon aerogels.The loading methods include one-step synthesis,sodium borohydride reduction and glycol reduction.And then the catalysts prepared by these methods were characterized by SEM.It was found that the Ag particles were loaded evenly on the carbon aerogel prepared by the ethylene glycol reduction method.The catalyst was also subjected to cyclic voltammetry in an electrolyte containing CO₂,and it was found that the catalyst prepared by the glycol reduction method had a best effect on CO₂ reduction.?2?The catalysts with different Ag loadings prepared by glycol reduction method were subjected to electrocatalytic reduction of CO₂.Platinum was used as the counter electrode.The reaction was carried out under different voltage conditions.It was found that CO₂ was best reducted at the mass ratio of AgNO₃/CA to 2:1.The yield of CO was 129.3?mol/h and the ratio of H₂ and CO was 1.9 at the reduction potential-1.6 V vs.SCE.The effect on CO₂electroreduction by different concentrations of electrolyte and pH of the solution were also investigated.It was suggested that the best reaction condition was at a electrolyte concentration of 0.5 mol/L NaHCO₃ and the pH value 8.Further more,the reduction of CO₂occurred more easily under high electrolyte concentration and alkaline conditions.?3?A solution containing NH₃ and a blank solution that does not contain NH₃ were used as the anolyte to perform electrochemical CO₂ reduction.The presence of NH₃ has a significant effect on the reduction of CO₂,and there was a different promotion for CO₂reduction under different voltages.However,the reduction effect of the system with NH₃present at-1.5 V vs SCE voltage is lower than that in the blank solution.