Synthesis Of Ethanol Electrocatalyst And Its Reaction Mechanism Research

The research of anode catalyst for direct ethanol fuel cell is very important for its commercial application,and it is also of significance to develop catalyst with high activity,stability,and high electrooxidation efficiency.The main products of ethanol oxidation are acetaldehyde and acetic acid.For rational designing of the catalyst to enable more efficient oxidation of ethanol to produce carbon dioxide,we study the ethanol oxidation mechanism and products' current efficiency.In this paper,we conduct the electrocatalyst structure design and composition engineering,and employ with differential electrochemical mass spectrometry method to analyze the effect of microstructure and composition on ethanol oxidation products and reaction mechanism,thus achieving the design of the catalyst.P-Pt-TiO₂-rGO composite as catalyst for ethanol electro-oxidation with three phase junction structure was synthesized by UV-photoreduction.XRD and TEM results indicate that photoreduction is favorable for anchoring Pt nanoparticles?NPs??ca.2.2 nm?at the interface between TiO₂ and reduced graphene oxide?rGO?,and for forming the Pt,TiO₂ and rGO three phase junction structure.P-Pt-TiO₂-rGO exhibits a higher activity for ethanol electro-oxidation than m-Pt/rGO and m-Pt-TiO₂-rGO?prepared by microwave-assisted polyol process?.Lifetime tests demonstrated that the electrochemical durability of p-Pt-TiO₂-rGO was improved by at least a factor of 2 as compared with m-Pt/rGO and m-Pt-TiO₂-rGO.XPS characterizations of p-Pt-TiO₂-rGO revealed stronger interaction between Pt and supports,when compared with m-Pt-TiO₂-rGO,which facilitates poisoning species removal and prevents Pt nanoparticles from migrating/agglomerating on or detaching from carbon support.In situ electrochemical mass spectrometry analysis showed that the close combination of platinum and titanium dioxide could promote the dissociation and adsorption of ethanol to form acetic acid,which was not conducive to the C-C bond breakage of ethanol.In order to improve the efficiency of ethanol electro-oxidation,we use tin dioxide instead of titanium dioxide as a carrier.The Pt/SnO₂/rGO electrocatalysts with platinum-tin dioxide-graphene three-phase contact structure was synthesized by L-arginine induction method.Firstly,the reaction between Sn2+ and the oxidation groups on the surface of oxided graphene were carried out.The graphene-containing tin dioxide nanoparticles composite was prepared by in situ redox reaction.The tin oxide nanoparticles were found to be uniformly dispersed on the surface of the graphene sheet;L-arginine as a protective agent and a linker,induced platinum nanoparticles in situ deposited around the tin dioxide nanoparticles,and prevented the agglomeration of platinum nanoparticles.The Pt/SnO₂/rGO electrocatalysts exhibited excellent electrocatalytic activity and stability.The electrocatalytic activity of Pt/SnO₂/rGO catalyst was determined to be 4.5 times of Pt/rGO.After 1000 cycles of aging,the electrocatalytic activity of Pt/SnO₂/rGO electrocatalyst was 69.6%,retained to be much higher than that of Pt/rGO.This was mainly attributed to the three-phase contact micro structure of Pt/SnO₂/rGO catalyst.In situ electrochemical mass spectrometry analysis showed that the Pt/SnO₂/rGO electrocatalyst was not conducive to the C-C bond breakage and complete oxidation of the ethanol molecules.The introduction of tin dioxide improved the current efficiency of acetaldehyde production,and reduced the current efficiency of acetic acid and carbon dioxide.In order to improve the efficiency of ethanol electrooxidation,SnO₂/Pt/rGO electrocatalyst with sandwich structure was designed and developed from the aspects of microstructure,and its effect on the reactivity and efficiency of ethanol oxidation was studied.The experimental results showed that the activity for the ethanol oxidation strongly depended on the contents of graphene and the highest catalytic activity occurs at?30 wt%,followed by?40 wt%,and?20 wt%.Electrochemical studies show that SnO₂/Pt/rGO electrocatalyst exhibited better electrocatalytic activity and stability than that of Pt/rGO.The electrocatalytic activity of SnO₂/Pt/rGO catalyst was determined to be 1.31.The retention rate of SnO₂/Pt/rGO electrocatalyst ethanol was 75.9%,which was much higher than 48.1%of Pt/rGO.This can be mainly attributed to the sandwich-like micro structure of SnO₂/Pt/rGO electrocatalyst.In situ electrochemical mass spectrometry analysis showed that the electrocatalyst SnO₂/Pt/rGO had the same carbon dioxide current efficiency as Pt/rGO.Compared with the three-phase contact structure Pt/SnO₂/rGO electrocatalyst,sandwich-liked SnO₂/Pt/rGO has stronger C-C bond breaking ability.This is because the sandwich-like micro structure promotes the further oxidation of acetaldehyde and acetic acid,and increases the chances of acetaldehyde and acetic acid re-entering the electrochemical reactivity zone,thus increasing the efficiency of generating carbon dioxide and acetic acid.In order to further improve the efficiency of ethanol electrooxidation,the influence of PtIr on the electrochemical oxidation efficiency of ethanol was studied.Ir has a very significant effect on the C-C bond breakage of ethanol molecules,and the current efficiency of platinum-iridium oxide on the formation of carbon dioxide was evaluated to be about 17%.