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[en] Density functional theory (DFT) computations were performed on the optimized geometric and electronic properties of reduced graphene oxide/polypyrole (rGO/ PPy) composite in comparison with pure graphene and graphene oxide structures. Incorporation of both reduced GO (rGO) and PPy will form a good composite which have advantages from both materials such as good mechanical strength and excellent electrical conductivity. These composite would be very suitable in fabrication of methanol sensor in direct methanol fuel cell (DMFC). The HOMO-LUMO energy (eV) was also calculated. These computations provide a theoretical explanation for the good performance of rGO/ PPy composite as electrode materials in methanol sensor. (author)
[en] This paper presents a silicon-based air-breathing micro direct methanol fuel cell (μDMFC) stack with a shared anode plate and two air-breathing cathode plates. Three kinds of anode plates featured by different methanol transport methods are designed and simulated. Microfabrication technologies, including double-side lithography and bulk-micromachining, are used to fabricate both anode and cathode silicon plates on the same wafer simultaneously. Three μDMFC stacks with different kinds of anodes are assembled, and characterized with a single cell together. Simulation and experimental results show that the μDMFC stack with fuel transport in a shared model has the best performance, and this stack achieves a power of 2.52 mW which is almost double that of a single cell of 1.28 mW
[en] World methanol uses, production capacity for 1996 to 2000, and the overall fundamental facts about methanol consumption and supply are reviewed. Results suggest that the use of methanol as a fuel is growing rapidly and it is also tied directly with the MTBE fuel oxygenate. Methanol is competing directly with liquefied natural gas, particularly as the average cash cost of production is decreasing. Fundamentals of methanol economics are outlined, showing that with minor exceptions, methanol pricing reflects commodity products in general. There is no historical reason to expect that these fundamentals will change in the near future. In view of that, the best strategy to maintain market share is to be the lowest cost producer, keeping up efforts to enlarge markets, focusing on reliability of the product, and on economics of scale, technology and finance. Reducing capital and operating cost, and paying close attention to freight costs are equally important strategy components. Issues concerning traditional gas purchasing strategies for North American chemical companies, factors responsible for gas price volatility, and approaches to gas purchasing are also addressed. tabs., figs
[en] The purpose of this project is to demonstrate the commercial viability of the Liquid Phase Methanol Process using coal-derived synthesis gas, a mixture of hydrogen and carbon monoxide. This report describes the proposed actions, alternative to the proposed action, the existing environment at the coal gasification plant at Kingsport, Tennessee, environmental impacts, regulatory requirements, offsite fuel testing, and DME addition to methanol production. Appendices include the air permit application, solid waste permits, water permit, existing air permits, agency correspondence, and Eastman and Air Products literature
[en] A passive, air-breathing 4-cell micro direct methanol fuel cell (μDMFC) stack is presented featured by a fuel delivery structure for a long-term and stable power supply. The fuel is reserved in a T shape tank and diffuses through the porous diffusion layer to the catalyst at anode. The stack has a maximum power output of 110mW with 3M methanol at room temperature and output a stable power even thought 5% fuel is the remained in reservoir. Its performance decreases less than 3% for 100 hours continuous work. As such, it is believed to be more applicable for powering the wireless sensor nodes
[en] Fuel cells offer one of the most promising technologies for the production of clean energy, both for transportation and for stationary production of electricity and heating. Currently, more than 100 billion m3 gas are flared each year because it has no market. If this gas were converted to methanol, the emission of greenhouse gases would be substantially reduced. Methanol is produced and distributed all over the globe and 99% of the infrastructure is present. Thus, if used as energy source for fuel cells, this may be the optimum solution for a clean environment. Although the concept is simple, a transition from a hydrocarbon-based economy to one based on hydrogen is a great technological and financial challenge. For the fuel cell technology to play an important role in energy production, it must be introduced on a large scale. This can be done by means of methanol
[en] The utilisation of biomass for methanol production via gasification faces the problem of a large excess carbon in the produced synthesis gas. The stoichiometric adjustment can be accomplished either by adding hydrogen or by removing carbon in form of carbon dioxide. The addition of hydrogen allows a nearly complete utilisation of the carbon contained in the biomass, with a high methanol production rate. But hydrogen admixture to the syngas requires supplementary investments for an electrolysis unit. The removal of carbon dioxide is less investment intensive, but due to the extremely low carbon conversion efficiency of about 20% of the biomass carbon content, the methanol production costs become very high. An acceptable way is a partial compensation of the carbon excess by adding electrolytic hydrogen (using the oxygen for the gasifying process), saving about half of the carbon from the biomass and avoiding extremely high investment and electricity costs. (Author)
[en] In this work, an active micro direct methanol fuel cell (μDMFC) system employing the catalytic combustor as the heating device is developed in order to maintain the optimum cell temperature and achieve the best cell performance. A passive feed method, combining both the saturator and the wick, is adopted to supply sufficient methanol into the micro combustor. The feasibility and the superiorities of the active μDMFC system are validated experimentally. The experimental results show that the combustor can start spontaneously and quickly at the ambient temperature of 298 K and the control unit can efficiently keep the cell temperature around the optimum value. The proposed active μDMFC system also performs much better than the conventional one at the ambient temperature of 298 K. Moreover, the performance and stability of the active μDMFC system at 298 K and the conventional one at 338 K are compared and analyzed respectively. The results verify that the active μDMFC system can real-time control the cell temperature and prevent overtemperature. Therefore, the active μDMFC system greatly increases the cell performance and stability. The active μDMFC system presented in this research also has great potential for portable applications. - Highlights: • A novel active μDMFC system is developed to solve the heat manage problem. • The micro catalytic combustor is employed as the heating device. • An electronic control unit is programmed to maintain the optimum cell temperature. • The presented active μDMFC system shows better performance and great stability.
[en] Highlights: • A simple hot-mould-modified Nafion membrane is used for direct methanol fuel cells. • Regular spindle-type groove array is uniformly distributed on the membrane surface. • Modification lowers methanol crossover, swelling, and improves proton conductivity. • Power density and long-time running performance of fuel cells are improved visibly. • This method provides a practicable way for direct methanol fuel cell applications. - Abstract: To lower methanol crossover and volume swelling degree, and to improve proton conductivity, a simple hot-mould-modifying method has been introduced to modify Nafion membrane for the direct methanol fuel cell application. To evaluate effect of the modification on properties of the Nafion membrane and fuel cell performance, a series of measurements of membranes and fuel cells have been carried out. The results show that, compared with the normal membrane, the modified Nafion membrane with regular spindle-type groove array possesses higher proton conductivity and methanol diffusion resistance, and 31.9% better dimensional stability, owing to its larger electrical double-layer capacitance come from the higher contact area between electron-electrode and ion electrolyte, and its more compact internal structure. And also, the direct methanol fuel cell based on the modified Nafion membrane shows 13.3% higher discharge power density and better long-time running performance than the normal one. Furthermore, this hot-mould-modifying method could be introduced into doping/coating-modified membranes reported in the current literature to further modify Nafion membranes, because this method is compatible with the current modifications.
[en] The engineering of electrocatalysts with high performance for cathodic and/or anodic catalytic reactions is of great urgency for the development of direct methanol fuel cells. Pt-based bimetallic alloys have recently received considerable attention in the field of fuel cells because of their superior catalytic performance towards both fuel molecule electro-oxidation and oxygen reduction. In this work, bimetallic PtCo mesoporous nanospheres (PtCo MNs) with uniform size and morphology have been prepared by a one-step method with a high yield. The as-made PtCo MNs show superior catalytic activities for both oxygen reduction reaction and methanol oxidation reaction relative to Pt MNs and commercial Pt/C catalyst, attributed to their mesoporous structure and bimetallic composition. (paper)