The Preparation And Research Of Electrode For Catalyzing Organic Small Molecules

Polyaniline（PANI） has catalytic effect on methanol electrooxidation. It has beenproved that PANI used as support materials for metal platinum and ruthenium catalyzercan increase the catalytic efficiency of methanol electrooxidation. The existence ofPANI in the catalyst layer of methanol oxidation electrode helps water absorption onthe catalyst, formation of an active oxycompound Pt-OHads which will promote COoxidation to CO₂. It also accelerates the Langmuir absorption behavior of methanol.However, despite what a conducting PANI can offer as a support material inelectrocatalysis, some disadvantages still limit its use in eletrocatalysis, such as loosemorphology, degradation and hydrolysis in solution and insufficient electronconductivity. On the other hand, carbon nanotubes （CNTs） as catalyst matrix have goodperformance of high surface area and high conductivity. The electrical conductivityand mechanical properties of the complex materials can be improved after introducingCNTs into the polyaniline. Using PANI/MWCNTs as metal catalyst platinum andruthenium carrier materials can not only improve the efficiency of catalysis, but alsoovercome the shortage of PANI, then the improvement of PANI can make it to beextensive potential in application.In this paper, firstly we prepared Pt-PANI and PtRu-PANI electrodes using PANIas support materials and separately discussed the optimum parameter and influencefactors for preparing. The electrocatalytic activity and morphology of the electrodeswere characterized using different methods. Secondly, we prepared Pt-PANI/MWCNTsand PtRu-PANI/MWCNTs electrodes using PANI/MWCNTs as support materials andseparately studied the process and influence factors for preparing. Also theelectrocatalytic activity and morphology of the electrodes were characterized usingdifferent methods.Pt-PANI was prepared by constant potential method for electrodepositon of Ptnanoparticles on PANI films which were prepared by in-situ electropolymerization ofaniline on platinum disk electrode. Cyclic voltammograms （CV） of Pt-PANI electrodesin methanol or formaldehyde solution showed that Pt-PANI perform higherelectrocatalytic activity than pure Pt electrode. The optimum thickness of PANI film,deposition potential and deposition times of preparation were studied and discussed.Scanning electron microscopy （SEM） was also employed to morphological study of the modified catalyst layer.Pt-PANI/MWCNTs was prepared by double potential step method forelectrodepositon of Pt nanoparticles on PANI/MWCNTs composite films which wereprepared by in-situ electropolymerization of aniline containing well-dissolvedMWCNTs on platinum disk electrode. CV of Pt-PANI/MWCNTs electrodes inmethanol or formaldehyde solution showed that Pt-PANI/MWCNTs performed higherelectrocatalytic activity than Pt-PANI electrode. We studied and discussed the optimumelectrodeposition potential of preparation, according to which we deposited Ptnanoparticles by double potential step method. The results showed that the electrodeprepared by double potential step performed higher electrocatalytic activity thanconstant potential method. We also characterized the electrode morphology andstability by SEM, FTIR spectra and chronoamperograms.We used pure PANI film as carrier material and prepared PtRu-PANI by doublepotential step method for Pt and Ru nanoparticles codeposition in the solution whichcontained H2PtCl6and RuCl3. CV of PtRu-PANI electrodes in methanol orformaldehyde solution showed that PtRu-PANI performed higher electrocatalyticactivity than Pt-PANI electrode. SEM and anenergy-dispersive X-ray analyzer （EDX）both showed that Pt and Ru particles achieved codeposition.We used PANI/MWCNTs film as carrier material and preparedPtRu-PANI/MWCNTs by double potential step method for Pt and Ru nanoparticlescodeposition in the solution which contained H2PtCl6and RuCl3. CV ofPtRu-PANI/MWCNTs electrodes in methanol or formaldehyde solution showed thatPtRu-PANI perform higher electrocatalytic activity than PtRu-PANI electrode. SEMand EDX both showed that not only Pt and Ru particles achieve codeposition on thecarrier materials, but also the particles of PtRu alloy had very unification diametersand dispersed very uniform.