A Study On Electrocatalytic Formaldehyde To Ethylene Glycol Reaction On Hydrophobic Carbon Electrode

Serving as a precursor of polyester compounds,Ethylene glycol has played an important role in our daily life.At present,ethylene glycol is primarily produced from petroleum-derived ethylene via epoxidation and subsequent hydrolysis of ethylene epoxide.At the same time,the synthesis route based on non-petroleum carbon resources was also developed,such as the hydrogenolysis of dimethyl oxalate and the carbonylation of formaldehyde followed by esterification and hydrogenation,these are multi-step processes that consume a lot of energy.The development of a new method for the direct synthesis of C2 compounds from C1 feedstock would be highly attractive.Therefore,on the basis of renewable energy and using C1 molecular formaldehyde as raw material,we studied the process of formaldehyde C-C coupling to ethylene glycol by means of electrocatalysis.Differing from traditional graphite electrode used in electrocatalytic formaldehyde C-C coupling,a cheaper and modifiable electrode,the carbon fiber paper(CFP),is used as the electroncatalyst in this work.In order to reach an effective and stable ethylene glycol production,for the first time,we hydrophobized the CFP to prohibit the deactivation of electrode and competing hydrogen evolution reaction.Specifically,we deposited PF on the surface of CFP though impregnation.It concluded that the hydrophobic carbon fiber paper inhibited the occurrence of hydrogen evolution during electrocatalysis process,meanwhile enhancing the stability of the electrode and the selectivity of ethylene glycol products.Furthermore,we regulated the hydrophobicity of the electrodes by adjusting the deposition amount of PF.Moreover,by correlating the electrocatalytic C-C coupling performance with HER tests,we established the relationship of hydrophobicity,hydrogenicity and catalytic C-C coupling stability of the electrode.In order to enhance the conductivity of the hydrophobic electrode modified by PF deposits,we added a certain proportion of nano-size graphite powder to PF emulsion and constructed a hydrophobic carbon layer on the surface of carbon fiber paper.As a result,a higher yield of ethylene glycol as well as the electrocatalytic stability is achieved.Besides,the ratio of C/PF in the hydrophobic carbon layer and the modification process were explored.When the carbon fiber paper surface was modified by the scraping method,and the mass ratio of C/PF in the hydrophobic carbon layer was 1/10,it show the best catalytic performance.In addition,we study the reaction conditions based on these two kinds of physically modified of CFP electrodes,and obtained the highest ever yield of electrocatalytic formaldehyde to ethylene glycol reaction within 10 h,with the average Faraday efficiency of 75%.