The Perparation And Research Of Platinum Composite Electrocatalyst For DMFC

Fuel cells are widely researched in recent years. But the catalyst materials are expensive and the intermediate products of oxidation poison the catalyst during catalytic process. What is more, catalyst will collapse and reunion and affect the activity of catalysts and service life. In order to improve the catalytic activity and long-term stability of the catalyst, codeposition ternary catalyst PtNiW/C and composite electrocatalyst Pt/Ni-WC/nD were prepared throgh the microwave assisted glycol reduction method. The structure and morphology of electrocatalyst was studied by X-ray diffraction(XRD) and transmission electron microscopy(TEM). The catalytic activity and the stability of the catalysts for methanol oxidation(MOR) and oxygen reduction reaction(ORR) were investigated. The results showed that the PtNi W/C electrocatalyst had the highest catalytic activity and the best ability of poison tolerance than PtNi/C and Pt/C. The remained electrochemical surface area(ECSA) was the most and the half wave potential of ORR decreased the least of the PtNiW/C catalyst than Pt Ni/C and Pt/C before and after the accelerated durability tests(ADT), which turned out that the PtNiW/C electrocatalyst performanced the best stability for MOR and ORR.Then a hybrid of nickel and tungsten carbide on n-dianmond(Ni-WC/nD) was synthetized by microwave-assisted depositing Ni(W) hydroxide on carbon black and then carbothermally reducing under N2 atmosphere and the amorphous carbon translated to n-diamond(nD) due to catalysis of Ni(OH)x. Platinum(Pt) electrocatalysts were prepared using the prepared hybrid as a support. The composition, structure and morphology of the Pt/Ni-WC/nD electrocatalyst were characterized by XRD, TEM and X-ray photoelectron spectroscopy(XPS). The results showed that Pt dispersed evenly on the support and the structure of Ni-WC/nD had changed to shell structure from particles after deposited Pt nanoparticles, thus improving conductivity and affinity between the Ni-WC/nD and Pt nanoparticles.The catalytic activity and the stability of catalysts were studied for MOR and ORR,which were measured through CV, CA and LSV methods. The results showed that the Pt/Ni-WC/nD catalyst had a higher ECSA and a higher activity and stability for methanoloxidation. The catalysts are four electronic reactions and Pt/Ni-WC/nD electrocatalyst has a higher initial potential and half wave potential than Pt/C, which proved a better catalytic activity for ORR. After scanning 3500 cycles, the remained ECSA was the most and the half wave potential of ORR decreased the least of the Pt/Ni-WC/nD electrocatalyst before and after the ADT and there were little migration and aggregation of Pt nanoparticles on the support. So it could be seen that the Pt/Ni-WC/nD catalyst has better long-term stability. The Pt/Ni-WC/nD exhibited better electrocatalytic activity and stability either for MOR and ORR. The superior electrocatalytic performance of Pt/Ni-WC/nD than Pt/C was ascribed to a high dispersion of Pt nanoparticles on the Ni-WC/nD support and the anchored structure and the synergistic effect between Pt and Ni-WC/nD support. At the same time, the Pt/Ni-WC/nD electrocatalyst improved the utilization rate of Pt.