Electrocatalytic Oxidation Of Small Molecules Of Organic Fuels On Pt And Pd Supported Carbon Materials And Conducting Polymer Composite Electrodes

With the increasingly serious environmental problems caused by fossil fuels,the development of new energy has received great attention.As one of the new energy sources,fuel cell has the advantages of low emission,zero pollution and high energy density.Among them,direct methanol fuel cell?DMFCs?and direct formic acid fuel cells?DFAFCs?have attracted extensive attention due to their easy access to raw materials,storage and transportation.The main components of anode electrocatalytic oxidation catalysts commonly used in direct methanol fuel cell and direct formic acid fuel cell are precious metal platinum?Pt?and platinum-based materials,but Pt catalyst is easy to absorb CO_ads produced by electrocatalytic oxidation of organic small molecules,which leads to the poisoning of Pt.The commercialization of direct methanol fuel cell and direct formic acid fuel cell needs to reduce costs and improve efficiency,so their commercialization process has been hindered.In order to reduce the cost of the catalysts,Pt can be replaced by other catalysts,such as Pd or Pt alloys.Carbon materials with good conductivity and high specific surface area,such as graphene and activated carbon,can also be used as support materials to support Pt,Pd or other catalysts to improve the utilization rate of catalysts.Of course,in addition to carbon materials,conductive polymers can also be used as support materials.Conducting polymers such as polyaniline and poly-o-methoxyaniline have unique conjugated electronic structures and good chemical stability.Support materials for catalysts can also improve catalyst utilization and electrocatalytic oxidation efficiency.In this work,first of allthe prepared carbon-coated silicon?Si@C?material was used to dope the carbon paste electrode to obtain the CPE-Si@C?X%?electrodes with X%weight percent Si@C.Pt/CPE-Si@C?X%?electrodes were obtained after loading Pt and applied to the electrocatalytic oxidation of methanol.Secondly,the prepared activated carbon?YBC?doped carbon paste electrode?YBCPE?12%??containing 12%weight percent activated carbonas modified with poly-o-methoxyaniline?POA?using electrochemical method to obtain the POA modified electrode POA/YBCPE?12%?.The Pd/POA/YBCPE?12%?composite electrode prepared by potentiostatic electrodeposition of Pd on POA/YBCPE?12%?was studied on electrocatalytic oxidation of methanol in alkaline medium.The effect of the Pd electrodeposition potential on the electrode electrocatalytic oxidation of methanol was explored.Then the electrocatalytic oxidation activity toward formic acid by various composite electrodes was studied,and the effects of electrolytic potential,film thickness of POA,and concentration of OAduring preparing the electrode POA/YBCPE?12%?on the electrooxidation activity of formic acid were explored.Finally,the influence of the proportion ofactivated carbon in Pd/YBCPE?X%?on electrocatalytic oxidation of formaldehyde onPd/YBCPE?X%?composite electrodes after doped carbon paste electrode?YBCPE?X%??loaded with Pd was investigated,and the effect of POA of Pd/POA/YBCPE?X%?on electrocatalytic oxidation of formaldehyde was investigated in detail.The research contents of this work are as follows:?1?Study on the Pd nanoparticles ontheactivated carbon dopedcarbon paste electrode torwardelectrocatalytic oxidation methanol in alkaline solutionThe composite electrodes of Pd/YBCPE?12%-100?,Pd/YBCPE?12%-200?and Pd/YBCPE?12%-300?obtained by electrode electrodeposition of Pd nanoparticles on the YBCPE?12%?electrode at different potentials of-100mv,-200mv and-300mv,respectively.And these electrodes were used to study the electrocatalytic oxidation of methanol in alkaline solution.The results show that Pd/YBCPE?12%-200?electrode had the best electrocatalytic activity for methanol electrooxidation.Then the YBCPE?12%?was modified with POA to obtain POA/YBCPE?12%?,and thePd/POA/YBCPE?12%-200?electrode was obtained by loading Pd on POA/YBCPE?12%-200?using potentiostatic method,and its activity toward electrocatalytic oxidation of methanol was studied.By comparing the electrocatalytic oxidation activity of Pd/YBCPE?12%-200?and Pd/POA/YBCPE?12%-200?for electrooxidation of methanol in alkaline solution,it was found that the electrocatalytic oxidation activity of Pd/POA/YBCPE?12%-200?was better,and the peak current density in CV in methanol solution for electrooxidation was 628.7 Ag^-1.The study of electrochemical impedance spectroscopy?EIS?in methanol solution showed that the charge transfer resistance of Pd/POA/YBCPE?12%-200?was small,and the Pd/POA/YBCPE?12%-200?had better stability and stronger poisoning resistance by chronoamperometry.?2?Study on electrocatalytic oxidation of formic acid with Pd/activated carbon/conductive polymer carbon paste composite electrodeThe POA/CPE and POA/YBCPE?12%?was obtained by modifying the CPE and YBCPE?12%?with POA,and then thePd/CPE,Pd/YBCPE?12%?,Pd/POA/CPE and Pd/POA/YBCPE?12%?were obtained by loading Pdusing potentiostatic method,respectively.These electrodes were used to study electrooxidation of formic acid.It was found that the Pd/POA/YBCPE?12%?had the best activity,the oxidation peakcurrent density of forward potential scan in the CV in the formic acid solution was1824A g^-1,whichis higher than that on other electrodes in the literature.The electrochemicalproperties of Pd/CPE,Pd/YBCPE?12%?,Pd/POA/CPE and Pd/POA/YBCPE?12%?were studied by a series of electrochemical tests.Finally,the effects of the electropolymerization potential of OA,OA monomer concentration and film thickness of POA on the electrocatalytic oxidation of formic acid onPd/POA/YBCPE?12%?wereinvestigated.The results show thatwhen the polymerization potential of OA was 700 mV,the OA monomer concentration was 20mM,and the polymerization charge was 16 mC,the Pd/POA/YBCPE?12%?had the best electrocatalytic activity toward formic acid oxidation?3?Electrocatalytic oxidation of methanol oncarbon-coated silicon composite doped carbon paste electrodeThe prepared carbon-coated silicon?Si@C?material was used to dope the carbon paste electrode to obtain the CPE-Si@C electrode.The electrochemical impedance spectroscopy?EIS?was performed on the prepared CPE-Si@C and CPE electrodes,and the results show that the CPE-Si@C?10%?electrode has a smaller charge transfer resistance.Pt/CPE and Pt/CPE-Si@C?10%?electrodes were prepared by electrodepositing Pt particlesusing potentiostatic method,and the obtained electrodes were used for electrocatalytic oxidation of methanol in acid media.The results show that the activity of Pt/CPE-Si@C electrode for electrocatalytic oxidation of methanol was higher than that of Pt/CPE electrode,and CPE-Si@C?10%?electrode electrocatalytic oxidation of methanol mass current density of 257mA mg^-1,which are1.8 times higher than that of Pt/CPE electrode.The Pt/CPE-Si@C?10%?electrode and the Pt/CPE electrode were characterized by chronoamperometry.The results show that Pt/CPE-Si@C?10%?has better stability and stronger poisoning resistance.?4?Study on Pd/YBCPE?X%?electrooxidation of formaldehyde in acidic solutionFirstly,the activity of electrocatalytic oxidation of formaldehyde by Pd/YBCPE?X%?was investigated,and it was found that the Pd/YBCPE?6%?had the best electrocatalytic oxidation activity.Then uisng electropolymerization method,POA filmswere prepared on the surface ofthe prepared CPE and YBCPE?6%?to obtain the electrodes of POA?16mC?/CPE andPOA?16mC?/YBCPE?6%?.Then Pd/POA?16mC?/CPE and Pd/POA?16mC?/YBCPE?6%?,which were obtained using potentiostatic electrodeposition of Pd on them,were uesd for the study of electrocatalytic oxidation of formaldehyde.The influence of the film thickness of POA in the Pd/POA/CPE and Pd/POA/YBCPE?6%?on the electrocatalytic oxidation of formaldehydewas investigated.The electrochemical properties of Pd/CPE,Pd/YBCPE?6%?,Pd/POA?16mC?/CPE and Pd/POA?16mC?/YBCPE?6%?were assessed by electrochemical tests.And the charge transfer of Pd/CPE,Pd/YBCPE?16mC?/YBCPE?6%?were evaluated by EIS.The resultsindicatethat Pd/POA?16mC?/YBCPE?6%?had the best activity,high stability and strong poisoning resistance.