Preparation And Electrocatalytic Properties Of Composite Catalysts With High Catalytic Performance And Low - Platinum Carrier Fuel Cells

Precious metal Pt and its composites is the widely used cathode and anode electronic catalysts in fuel cells. But there are still many serious problems to use Pt as fuel cell catalyst:（1） the deficiency of Pt resources;（2） the price of Pt is rather expensive;（3） the inferior ability of anti-poison. Therefore lowing the usage amount of Pt and improving activity of the catalysts is still necessary. Recombination of Pt with other materials can improve its catalytic ability and anti-poison ability meanwhile lowing the usage amount of Pt, solving this problem effectively.This paper aims at studying on preparing fuel cell catalysts with high catalytic efficiency and low usage amount of Pt, in addition testing its corresponding catalytic performance. We have prepared nanoporous gold loading Pt/Sb₂O₃ catalysts respectively through the use of electrochemical deposition. With nanoporous gold（NPG） as carrier and H2 PtC l6, SbCl3 as precursors, cyclic voltammetry（CV） and linear sweep（LS） are used respectively to deposite Pt and Sb on NPG. NPG/Pt（Sb₂O₃） catalysts are prepared and characterized by X-ray powder diffraction（XRD） and scanning electronic microscope（SEM） to test the structure and surface properties of the catalysts. XRD results show the NPG/Pt（Sb₂O₃） catalysts are prepared successfully. SEM results display Sb₂O₃ grow extensively on the surface of NPG/Pt and exhibit nice morphology with well dispersity as well as good continuity and integrity. Single cell is assembled and electrochemical workstation is used to test its electrochemical performance. The catalytic properties toward oxygen reduction reaction of NPG/Pt（Sb₂O₃） catalysts is focused as well as catalytic performance toward methanol. Results show that NPG/Pt（Sb₂O₃） catalysts exhibit well catalytic activity as cathode catalysts. Mainly reflecting in the limiting diffusion current is obviously higher compared with pure NPG/Pt, while the onset potential is not lower than NPG/Pt. Meantime, compared with pure NPG/Pt catalyst, NPG/Pt（Sb₂O₃） catalyst shows higher electron transferred number and higher kinetic current density. Indicating the ORR activities of the catalysts are improved effectively with Sb₂O₃ as the assistant catalysts. C yclic voltammetry results show NPG/Pt（Sb₂O₃） catalysts exhibit better catalytic activity to methanol in acid solution than NPG/Pt.Secondly, using nanoporous gold（NPG） membrane as the carrier, NPG/Pt Ru catalysts are prepared with electrochemical deposition. Firstly, under potential deposition（UPD） method is adopted to deposit Pt on the surface of nanoporous gold（NPG） membrane in electroplate solution of chloroplatinic acid（H2PtC l6）. Then, linear sweep method is used todeposit Ru on the surface of NPG/Pt in electroplate solution of ruthenium trichloride solution. The scanning is measured for eight time s. The scanning times is used to change the quantity of Ru. NPG/PtRu catalyst with different scanning times is prepared. X-ray powder diffraction 、scanning electronic microscope and energy spectrum analysis method are measured to characterize the catalysts. The catalytic performance toward methanol is tested through electrochemical workstation. NPG/Pt Ru catalyst exhibit better catalysis performance toward methanol than NPG/Pt. NPG/PtRu catalyst with six scanning times exhibits best catalytic activity, with the lowest onset potential and the biggest peak current. The addition of Ru changes the catalytic activity and anti-poison property and improves catalytic performance of the catalyst.In addition, PtC u/C alloy catalysts with high activity、low usage amount of Pt are prepared. Microwave reduction method is used to prepare PtC u/C binary alloy catalysts of which the theoretical atomic ratio of Pt and C u is 1:1, 1:2, 1:3, 2:1, 3:1, 4:1. The catalytic performance of PtC u/C alloy catalysts with different atomic ratio toward methanol, alcohol and formic acid as well as oxygen reduction reaction activity are tested. Transmission electronic microscope（TEM） 、 X-ray diffraction（XRD）、 cyclic voltammetry（C V）、amperometric i-t curve are used to analyze the morphology、structure and electrochemical properties in detail. Electrochemical measurement results show that PtC u/C alloy catalyst with the atomic ratio of 1:1 exhibits superior electronic catalytic activity towards methanol、formic acid and alcohol as anode catalyst. The catalyst with the atomic ratio of 2:1 expresses better oxygen reduction reaction activity than Pt/C catalyst with the same content of Pt. Mainly reflecting in the obviously bigger onset potential and markedly improved peak current. The main reason lies in the surface character of Pt is changed with the addition of C u. The specific area is enlarged and dispersity and availabibility of Pt are improved. Thus the catalytic performance of oxygen reduction reaction is enhanced.