Different Solvents Pyrolytic Synthesis Multi-walled Carbon Nanotubes Supported Pd-based、Pt-based Binary Metal Catalyst For Formic Acid And Ethanol Oxidation

Energy resources are the basis of energy development. In recent years, with therapid development of society and technology, demands for energy in the human areincreasing. In addition, environmental pollution problems are increasing too. Sorenewable energy and environmental protection have become a hot topic all over theworld. Although our country is relatively abundant in fossil energy resources, but lessper capita and development are difficult. So the development of new renewable greenenergy is of increasingly important. Fuel cell is a kind of device used to convertchemical energy into efficient environmentally friendly energy sources in theisothermal environment convert. It is a new type of green power generation device andstudy more efficient fuel cell catalysts is of particularly important. Research Findings,noble metal Pd and Pt has good catalytic performance for formic acid and ethanoloxidation. But its high cost is not suitable for industrial production. In the presentpaper, we with the room temperature ionic liquid and water as the solvent, adopt themethod of direct pyrolysis to synthesize of Pd based and Pt based catalyst particlessupported on multi-walled carbon nanotubes (MWCNTs). Its catalytic properties forformic acid and ethanol oxidation are studied. The catalysts were characterized byX-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electronmicroscopy (SEM) and energy dispersive spectroscopy (EDS), Electrochemical testswere carried out by cyclic voltammeters (CV), impedance (EIS), chronopotentiometry(v-t) and chronoamperometry (i-t), for the preparation of a variety ofcatalysts.The main experiment as follows:1. With the room temperature ionic liquid (BPyBF4) as solvent, This experimentadopted the method of direct pyrolysis to synthesis of Pd-Ni/MWCNTs catalysts andstudied the different proportion of Pd Ni atoms(1:0、1:1、1.5:1、2:1) for effect offormic acid catalytic oxidation, in order to prove the most suitable atomic ratio. Usingthe XRD to test the PdxNiy/MWCNTs particles and the results showed that Pd-Ninanoparticles are successfully adhere to the surface of MWCNTs and calculated the average particle size. The smallest size sample is Pd3Ni2/MWCNTs, a diameter ofaround7.6nm. EDS proved the existence of metal Pd, Ni on the surface of theMWCNTs. SEM、TEM photographs are further evidence that the Pd, Ni metal particlesuniform distribution to the surface of carbon nanotubes. The test by cyclicvoltammograms and other electrochemical methods proves that in acidic conditions,Pd/MWCNTs and Pd-Ni/MWCNTs showed the highest electrocatalytic activity forformic acid oxidation, but Pd-Ni binary metallic catalytic performance is obviouslybetter than that of pure metal Pd. And the study found that the proportion of differentPd, Ni catalyst of formic acid catalytic activity is different,Pd3Ni2/MWCNTs is thebest. This is consistent with XRD and other characterization results.2. Still with the method of direct pyrolysis synthesis Pd/MWCNTs catalysts inroom temperature ionic liquid ([OMIM]Br), the deionized water as solvent(thevolume ratio of3:1), it studied the different pyrolysis time impact on the performanceof the ethanol catalyzed oxidation. XRD, TEM characterization of the morphologyproved that the metal Pd nanoparticles can successly grow on the surface ofmulti-walled carbon nanotubes. Researches revealed that the synthesis of Pd particlesunder the3h is minimal, about16nm and distribution on unit area of carbonnanotubes is the largest and the most uniform. The method of electrochemicalcharacterization also found that synthetic samples under the3h in alkaline conditionsto ethanol oxidation catalytic performance is best, because the catalyst of ethanoloxidation peak current of about17times the minimum current. So pyrolysis3h is thebest time.3. With the deionized water as solvent, the experiment adopted the method ofdirect pyrolysis to synthesis of Pt-Ni/MWCNTs catalysts and studied that different Niadding quantity (Pt, Ni atomic ratio respectively1:11:21:31:4) affects theperformance of catalyst. The structure and crystal types of the sample werecharacterized by SEM,TEM and XRD. The electrocatalytic performance of thesample toward ethanol oxidation was examined by cyclic voltammetry (CV),chronoamperometry(i-t), AC Impedance(EIS). Results showed that through thehydrothermal method to the success of the metal Pt-Ni particles modification to the surface of MWCNTs and found that under the condition of alkaline Pt: Ni=1:3samples for ethanol catalytic oxidation performance is the best. Observation ofSEM,TEM photographs can also see the minimum sample size on the surface ofMWCNTs dispersed quantity and uniform.4. Continuing with the room temperature ionic liquid (BPyBF4) as solvent, theexperiment adopted the method of direct pyrolysis synthesized multi-walled carbonnanotubes (MWCNTs) load Pd particles catalysts under different temperatures of100oC,200oC and300oC. By XRD confirmed, producing the metal particles of Pd,and measured the average particle size, results indicate that the sample synthesizedunder200oC has the smallest size is17.0nm and further determined by EDS test theXRD test results. The SEM and TEM photos can show the existence of the metalparticles on the surface of MWCNTs after pyrolysis, and the sample synthesizedunder200oC is minimal. Under acidic conditions, the formic acid catalytic oxidationactivity with the catalysts, synthesised under different temperature, were investigatedby using cyclic voltammetry (CV), chronoamperometry(i-t), AC Impedance(EIS), andthe results showed that samples synthesized under200oC has the best catalytic activity.The result is the same as the conclusions of XRD, SEM characterization methods.