| In today’s world, the demand for clean and sustainable energy sources has become a strong driving force in continuing economic development, and thus as well in the improvement of human living conditions. Direct methanol fuel cells (DMFC), as clean energy-converting devices, have drawn a great deal of attention in recent years due to their high efficiency, high energy density, and low or zero emissions. However, the low electrochemical activity and high cost of the electrocatalysts are still the key issues hindering the commercial application of fuel cell. Therefore, the improvement of the electrocatalytic activity and the durability of the electrocatalysts as well as the decrease of the cost are the effective routes for the commercial application of fuel cells.In this dissertation, the nitrogen doped methods, the assistant catalysts (metal oxides), new structure of classical catalysts and new catalyst supports in fuel cells have been developed and investigated. The micrographs, structure and properties of the catalysts applications have been investigated by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD). Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES). elemental analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), linear sweep voltammetry (LSV), cyclic voltammetry (CV), chronoamperometry (CA) method, etc. The aims for this dissertation are summarized as follows:(1) The nitrogen-doped hollow macroporous carbon spheres (NHMCS) were synthesized by silica template using3-ethyl-1-vinylimidazolium tetrafluoroborate ([VEIM]BF4) as the source of carbon and nitrogen. The as prepared NHMCS were characterized by SEM, TEM, BET and elemental analysis. The results show that NHMCS have the ordered macroporous structure, high-surface-area as well as1.4%nitrogen doped content. The typical electrochemical methods were used to study the activity of NHMCS for oxygen reduction reaction in alkaline media, and the results also show that NHMCS possess better electrocatalytic activity and higher resistance to the methanol crossover compared with commercial Pt/C via a four-electron pathway. (2) Selecting the NHMCS as supporting materials, Pt or PtRu NPs with high dispersion and small particle size were successfully supported on the NHMCS surface by a microwave assisted polyol reduction method. The micrograph of Pt/NHMCS and PtRu/NHMCS nanohybrids and their electrocatalytic properties for methanol oxidation were characterized by TEM and CV, respectively. The results show the NHMCS possess a high surface area, good conductivity, and porosity suitable for mass transport, and they can be used as a support for Pt electrocatalysts. The TEM results show Pt (PtRu) nanoparticles with an average size of2.64nm (2.49nm) are homogeneously distributed onto the NHMCS. The obtained Pt/NHMCS and PtRu/NHMCS exhibit a significant catalytic activity for the oxidation of methanol than E-TEK Pt/C and PtRu/C.(3) A green and low-cost strategy for synthesis of Pt-SnO2/carbon nanotubes (CNTs) with SnO2-around-Pt structure by in situ spontaneous reducing PtCl62-with Sn2+on the CNT surface is developed. The morphology and structure of Pt-SnO2/CNTs nanocomposites were characterized by TEM and XRD. EDS and ICP-AES results show that the molar ratio of Pt to SnO2in SnO2-Pt/CNTs is approximately0.48. Compared with the commercial Pt/C (E-TEK), SnO2-Pt/CNTs electrocatalyst exhibits higher electrocatalytic mass activity and better long-term cycle stability for methanol oxidation. |
PDF Full Text Request