Advanced Materials Research Vols. 860-863

Abstract: A diverse sulfonated polybenzimidazole copolymer (SPBI) as proton exchange membrane was synthesiszed via one-step high temperature polymerization method with 3,3-diaminobenzidine (DABD), 5-sulfoisophthalic acid (SIPA), 4,4-sulfonyldibenzoic acid (SDBA) and biphenyl-4,4-dicarboxylic acid (BDCA). The SPBI membrane was prepared through a direct hot-casting and in situ phase inversion technique. Characterization tests were carried out on the membranes including surface morphology, distribution of elements on the membrane, determination of functional groups, thermal stability, ion exchange capacity, water uptake rate and proton conductivity. The as-synthesized SPBI membrane displayed a smooth surface via scanning electron microscopy (SEM) analysis which is thermally stable up to 443 °C. The SPBI membrane showed higher water uptake rate (WUR) and proton conductivity though it had lower ion exchange capacity (IEC) value compared to recast Nafion membrane. The proton conductivity of the SPBI membrane with IEC of 0.60 mmol/g was 4.50 × 10^-2 S/cm at 90 °C. This study shows that the SPBI membrane has great potential in polymer exchange membrane fuel cell (PEMFC) applications.

Abstract: This study is focused on the elaboration of 8 mol.% yttria stabilized zirconia (YSZ) thin films onto porous supporting NiOYSZ anode substrates using pulsed laser deposition (PLD),and their microstructural and electrical characterizations. Better crystallinity and grain connectivity is observed increasing the deposition temperature until best values are obtained at 500°C. The greater relative conductivity enhancement is found at 300-500°C. The observed an increased conductivity at lower temperatures may be caused by a combination of nanoscaled effect of the YSZ thin film and interfacial effects between YSZ thin film and substrate.

Abstract: Fuel cell is one of the most promising power sources towards high-efficiency, low-emission and environmental benign application. In pursuit of a higher performance, electrocatalyst is a crucial research focus. Compared with commercial carbon support, TiO₂ exhibits the advantages of higher stability, higher porosity and stronger metal-support interaction. In this article, we give a brief overlook on the influence of diverse crystal and morphology structures on their eletrocatalytic property in fuel cells. Besides, to better meet the demand of practical electrocatalysts, three different methods are summarized to overcome its relatively poor electrical conductivity. Overall, TiO₂ is a promising support material of electrocatalysts in fuel cells.

Abstract: Electrodes, catalysts, membranes, if present, are three main components in constructing a MFC for harvesting desired maximum power density and achieving higher coulombic efficiency (CE). Great improvements have been made, based on previous researches, in developing and diversifying materials, aside from architectures. Electrodes most familiar to us are widely used carbon materials. For anodes, carbon matrix composites (e.g., acombination of polyaniline (PANI) with TiO2 using carbon as substrate) have gained special attention, though carbon material itself can exhibit excellent performance by diversifying molecular structures such as carbon nanotubes (CNTs). In the meanwhile, the evolution of MFC architectures, heading to the direction of improving power generation, contributes to the combination of membranes and cathodes from separate modes to diverse assemblies, on which all sorts of catalysts, such as from commonly used Pt to iron phthalocyanine (Pc), metal tetramethoxyphenylporphyrin (TMPP), MnOx, or pyrolyzed iron (ll) phthalocyanine (pyr-FePc), can immobilize through synthesis of these catalysts with polymer such as Nafion 117 (Dupont Co., USA) or tetrafluoroethylene (Teflon) containing functional groups or Polypyrrole (PPy). This paper is mainly aimed at reviewing the development of materials in recent years and making several proposals.

Abstract: In this study, aiming to obtain high performance nanocatalysts for NaBH₄ hydrolysis, Co₃Ni film composed of nanosheets with a mean thickness of 10 nm was fabricated by a magnetic field induced deposition process. X-ray diffraction analysis indicated that the as-prepared Co₃Ni film is presented in both face-centered cubic phase and hexagonal close-packed phase. The nanostructured Co₃Ni film catalyst showed good catalytic activity in the hydrolysis of NaBH₄ and the rate constant was 5.77 mL·min^-1. It was revealed that Co₃Ni film catalysts didnt lose their catalytic original activity essentially after 10 cycles, which exhibited much improved reusability and stability compared with with recently reported nanocatalysts.

Abstract: Direct ethanol fuel cells are considered a promising power source for future portable electronic and automotive applications. This article reviewed the synthetic methods commonly used to prepare Pd-based catalysts for the ethanol electrooxidation in alkaline media. The progress in the mechanism studies of ethanol oxidation reaction (EOR) on Pd electrode in alkaline medium by cyclic voltammetry and electrochemical in situ FTIR spectroscopy was also reviewed. The recent studies revealed that the EOR is fairly complicated, and it is difficult in CC bond cleavage for the complete oxidation of ethanol to CO₂, and ethanol is selectively oxidized to acetate on Pd-based catalysts in alkaline media. Overall, what is most important is to explore new Pd-based alloy catalysts with high ability to break the CC bond to promote complete oxidation of ethanol as well as increase the efficiency of DEFCs.

Abstract: This work studies the use of Multi-walled carbon nanotube (MWCNT) as catalyst supports for H₂O₂ electro-reduction in acid media. Using impregnation-chemical reduction method, we prepared Pt-Ag/CNTs, Pt-Co/CNTs, Pt-Ag/C and Pt-Co/C nanocatalysts. Four catalysts were analyzed by XRD and TEM. Their electrochemical performance was studied via cyclic voltammetry curve. The results show that: the nanoparticles have a better dispersion on CNTs substrate than on XC-72 carbon substrate. Comparing with Pt-Ag and Pt-Co on XC-72 carbon substrate, the H₂O₂ reduction reaction activation energy of catalysts on CNTs substrate is bigger, and the peak current densities of catalysts on CNTs substrate are larger than that on XC-72 carbon.

Abstract: To investigate the influence of ethanol catalyzed oxidation on activity of Pd/C with different ratio of Pd and C. Pd/C catalyst samples with Pd loads of 20, 30, 40 and 50 wt% were obtained by chemical reduction reaction of PdCl₂ and NaBH₄. The samples morphology and structure were characterized by XRD and SEM. The electrocatalytic oxidation activities of ethanol were examined by cyclic voltammetry in alkaline media. The results show that a face centered cubic (FCC) Pd phase can be identified in the sample powders. The average particle size of the Pd/C powder is about 10 nm. The performance of ethanol oxidation on 40 % Pd/C electro-catalyst is better than that of the other Pd/C samples.

Abstract: The significance of researching on fuel cell electrical vehicle (FCEV) DC/DC converter, FCEV driving system structure and requirement with DC/DC converter are introduced firstly. Some key problems of development in FCEV DC/DC converter are particularly analyzed, including of reliability, efficiency, static and dynamic characteristic, etc. The average efficiency of boost or buck circuit can reach more than 95%. The dynamic response time of DC/DC converter is below 160 ms. All kinds of DC/DC converters operate with zero error, and various technical indicators can satisfy the operating requirement. The converters are successfully used in china fuel cell city buses and technical indexes are fulfilled.

Abstract: SiO₂ antireflective films were prepared by two-step catalyzed sol-gel method with TEOS as the raw materials, acid and ammonia as catalyst. Effects of the ratio of acid-catalyzed and base-catalyzed silica sols on the transmittance and stability of SiO₂ film were investigated. The transmittance can be adjusted by change the ratio of base-catalyzed sols, and a higher transmittance can be obtained in the higher ratio of base-catalyzed coatings. A higher stability of SiO₂ film in salt spray can be obtained in higher ratio of acid-catalyzed AR coatings. AR coatings with excellent transmittance and stability can be obtained by adjusting the ratio of acid/base catalyzed silica sols.