Preparation Of High-performance Pt/C Catalysts By Microwave-assisted Ethylene Glycol Reduction

Proton exchange membrane fuel cells(PEMFC)have many advantages such as environmental-friendliness,low temperature,high power density,transportability,and convenience to control.Carbon-supported platinum nanoparticles(Pt/C)are the most popular electrocatalysts in PEMFC because of their outstanding electrocatalytic activity and durability.Pt/C catalysts can be synthesized by multiple approaches,such as the electrodeposition method,the hydrothermal method,the impregnation method,the polyol method,and the microwave-assisted method.Of the reported methods,the impregnation method is a relatively simple chemical synthesis.However,it is difficult to produce small nanoparticles.The polyol method achieves small particle size,but requires long reaction time and large energy consumption.The microwave-assisted method has many advantages,such as quick reaction process,short heating time,energy conservation and environmental protection.The microwave-assisted method can synthesize Pt/C catalysts rapidly with small particle sizes(2-4 um)and high dispersion.In previous work,the metal precursor and the carbon black were mixed together prior to microwave irradiation,which limited the efficiency of the reduction,because high concentrations of carbon black could cause explosion during microwave irradiation.In this work,high-performance Pt/C catalysts are prepared by an improved microwave-assisted ethylene glycol reduction.The platinum precursor is reduced first to obtain Pt nanocolloid(PNC).UV-visible spectroscopy shows that the microwave reduction process is completed in only 1 minute.Transmission electron microscopy(TEM)shows that the size of platinum nanoparticles in PNC is only 2.1 nm.Then Pt/C catalysts of 20.7 wt%,42.2 wt%and 60.9 wt%are prepared by reacting PNC with carbon black.Zeta(?)-potential test shows that the platinum nanoparticles settle on the carbon carrier after the mixture is adjusted to be acidic.The synthesized Pt/C catalysts are physically characterized using TEM,X-ray diffraction(XRD)and thermogravimetric analysis(TGA).TEM graphs show that the platinum nanoparticles are uniformly dispersed on the surface of the carbon support,and the average particle diameter of each catalyst is counted;TEM shows that the size of platinum nanoparticles is only 2-4 nm.XRD shows the variation of the platinum peak width with the different Pt loadings;TGA confirms that the actual platinum loadings of the catalysts are very similar to the theoretical platinum loadings.Catalyst activity is investigated using electrochemical and single cell tests.The self-made Pt/C catalysts exhibit excellent electroactivity due to small platinum nanoparticles;and the single cell tests also show the good performances of Pt/C catalysts in hydrogen/air flow.Additionally,a bulk amount of PNC is prepared at one time and stored in a refrigerator for 3 months.The 60.9 wt%Pt/C catalysts are synthesized every month using the PNC.Electrochemical characterization and ?-potential measurements confirm the good stability of the Pt nanocolloid,since performances of 60.9 wt%Pt/C catalysts remain almost unchanged during 3 months,which greatly improves the efficiency and convenience of preparing Pt/C catalysts as needed.All in all,this work offers an easy and rapid method to synthesize Pt/C catalysts and a scheme for preparing Pt/C catalysts in needed,which provides a certain guidance for the exploration of catalyst preparation,and helps to accelerate the commercialization of PEMFC.