Study On The Anodic Electrocatalysts For Direct Alcohol Fuel Cells

Direct alcohol fuel cell (DAFC) is a kind of technology for green power application which converts directly chemical energy to electric energy via the electrochemical technique. This green energy technology, with lots of advantages like the abundant sources, high energy transfer efficiency, the safety for the storage, transportation of the fuel and so on, is of great importance for sovling the problem of the energy crisis and environmental pollution. However, the primary problem is the low electrocatalytic activity of anodic catalysts for alcohol electro-oxidation. Hence, it is necessary to prepare high-efficiency supports to decrease the dosage of the novel metal Pt, which is also an effective way to reduce the cost of fuel cell. In this thesis, supports were treated via different process or modified with different materials and the related electrocatalysts were investigated for methanol and ethanol electro-oxidation in acid media.The main points in this thesis are presented as follows:1. Tannic acid can be attached to carbon nanotubes viaπ-πinteractions at room temperature. PtRu nanoparticles were successfully supported on the surface of Tannic acid modified multiwalled carbon nanotubes (TA-CNTs) through the microwave-assisted polyol method. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) results show that the PtRu nanoparticles homogeneously disperse on the surface of TA-CNTs. Electrochemical testing results indicate that the PtRu/TA-CNT electrocatalyst has an improve electro-catalytic activity and long-term stability for methanol oxidation reaction (MOR) compared with the PtRu/CNT electrocatalyst.2. Carbon encapsulated SnO2 (SnO2@C) composites were prepared by a thermal evaporation and decomposition of malic acid (C4H6O5) at low temperature (200℃) and demonstrated their potential use in direct ethanol fuel cells (DEFC). Energy disperse X-ray spectroscopy (EDS), Scaning electromicroscopy (SEM), TEM and XRD were used to characterize the elemental compositions and the morphology of the SnO2@C composite, respectively. The electrocatalytic activitities of the SnO2@C supported Pt catalyst (Pt/SnO2@C) for ethanol oxidation were studied in 0.5 M H2SO4+1.0 M CH3CH2OH solution by cyclic voltammetry. Under the same loading mass of Pt, the Pt/SnO2@C catalyst shows higher electrocatalytic activity and better long-term cycle stability than Pt/SnO2 catalyst due to the presence of carbon layer on the surface of the support.3. Carbon nanotubes (CNT) were treated by hydrofluoric acid (HF) and oxidated by H2O2 solution under microwave irradiation to prepare functional carbon nanotubes (f-CNT). The f-CNT supported bimetallic electrocatalyst (PtSn/f-CNT) was fabricated via NaBH4 reduction method and its catalytic activity for ethanol electro-oxidation was also investigated in acid media. The results indicate that the enhancement of the electrocatalytic activity is attributed to the f-CNT which can anchor metal nanopaticles and improve the dispersion of the electrocatalyst.