Preparation And Electrocatalytic Properties Of Supported Pt-Based Nanostructured Electrodes

Direct methanol fuel cell?DMFC?has been attracted wide attention due to its high energy density,low operating temperature and non-pollution.Compared with other catalysts,Pt or Pt-based alloys possess more excellent catalytic properties in methanol oxidation and are used as catalysts of DMFC basically.However,these catalysts are high cost and easy to be CO poisoning,which inhibits the DMFC's large-scale applications and industrialized development seriously.Therefore,the study on preparing nanostructured catalysts to reduce the amount of noble metal and relieve CO poisoning is of great importance.In this paper,Pt/TNTs,Pt/RuO₂/TNTs and PtRu/TNTs composite electrodes were fabricated by pulse electrodeposition using anodic TiO₂ nanotube arrays?TNTs?as carrier material.Effects of electrolyte components and electrochemical parameters on the morphology,composition,phase constitution of electrodes and their electrocatalytic properties and anti-CO poisoning properties were discussed via XRD,FESEM,EDS,XPS characterization and cyclic voltammetry measurements.The main results are as follows:In the third chapter,TNTs were used as carrier material,highly active Pt nanoparticle/TNTs composite electrode were prepared via impulse current deposition.Effects of the reductive doping and time were studied.The results show that Ti₃₊ is produced by the reductive doping of TNTs,which makes the resistance of TNTs efficiently decreased.The increased conductivity of TNTs facilitated the subsequent electrodeposition of Pt nanoparticles,leading to the smaller size of Pt particles and higher deposition rate,which improves the methanol oxidation catalytic performance of electrode significantly.Dynamic analysis results show that the transfer coefficient increases to 0.198.The Pt/reductive doped TNTs electrode prepared from 240 min electrodeposition exhibits excellent electrocatalytic activity.The peak current density of Pt/reductive doped TNTs electrode is as high as 76.6 mA/cm²,which increased by 60% compared with the Pt/untreated TNTs electrode.In the forth chapter,Pt/RuO₂/TNTs composite electrode were parpared using TNTs as carrier material via coating of RuO₂ and electrodeposition of Pt nanoparticles.Effects of RuO₂ layer on the catalytic activity,stability and anti-CO poisoning properties of composite electrodes were studied detailedly.Due to the existence of RuO₂ interlayer,charge transfer resistance Rct and inductance L decreased to 28.3?·cm² and 82.6 H·cm² by Electrochemical impedance spectroscopy measurement,which indicates that the interlayer RuO₂ not only promotes the oxidation of methanol but also efficiently inhibits Pt poisoning.For the Pt/RuO₂/TNTs composite electrode coated with RuO₂ for 5 times,its peak current density of methanol oxidation reaches 105 mA/cm² in solution containing 0.5 mol/L CH₃OH and 1 mol/L H₂SO₄ solution.After cyclic voltammetry scanning for 500 cycles,the peak current density of electrode coated with RuO₂ for 13 times still remains 96.7%,and onset current of CO oxidation appears in the low potential?0.4VSCE?,exhibiting excellent stability and anti-CO poisoning properties.In the fifth chapter,highly active PtRu alloys/TNTs composite electrodes were parpared by electrochemical co-deposition on TNTs carrier.The effects of PtRu molar ratio in electrolyte,the pulse potential,duty cycle,etc.,on catalytic performance and anti poisoning performance were studied.The optimal technology is to co-deposit of PtRu alloys in electrolyte with PtRu molar ratio of 5:1,and pulse deposition potential of 0.6 V,deposition time of 0.1 s,reversed dissolution potential of-0.1V,dissolution time of 0.9 s and duty cycle of 0.1.In this case,the PtRu atomic ratio of composit electode is 2:1,and the electrocatalytic properties and anti-CO poisoning properties of this electrode are better than these obtained in other conditions,the peak current density for methanol oxidation is 33.9 mA/cm².