Fuel cell unit of DMFC type and its operation

Abstract

In order to achieve a higher power density in a fuel cell of DMFC type, in which liquid methanol is oxidised to carbon dioxide and water, the methanol is in a first step (1) exposed to a first desired anodic reaction (a) while using a catalyst optimised for said first reaction, the reaction products from the first step are led to a second step (2) in which a second desired anodic reaction (b) is performed while using a catalyst optimised for said reaction, and the reaction products from the second step are led to a third step (3) in which a third desired anodic reaction (c) is performed while using a catalyst optimised for said third reaction. The three reaction steps are suitably conducted in three cells (1, 2, 3) that are connected flow- wise in series in a fuel cell unit and the supply of oxidant to the different steps is suitably controlled such that the reactions on the anodic and the cathodic sides are in stoichiometric balance with each other in every single step. Thereby, the reactions can be more reliably refined and controlled in order to increase yield. Hydrogen peroxide is preferably used as oxidant. By connecting two such fuel cell units flow- wise in series, liquid ethanol can be used as fuel. In the first unit, the ethanol is oxidised to carbon dioxide and methanol and in the second unit the methanol is oxidised to carbon dioxide and water.

Description

technical field [0001] The present invention relates to the operation method of DMFC type fuel cell, wherein general formula RCH 2 Oxidation of aliphatic short-chain water-soluble liquid alcohols of OH, aldehydes of the general formula RCHO or acids of the general formula RCOOH to carbon dioxide and water, where R represents H, CH 3 、C 2 h 5 or C 3 h 7 . [0002] The invention also relates to a fuel cell device of the DMFC type comprising: an anode side having an anode and a catalyst for the anode reaction, a cathode side having a cathode and a catalyst for the cathode reaction, and separating the anode side and the cathode side from each other open interlayer. Background technique [0003] Fuel cells driven by direct methanol are previously known, see e.g. http: / / www.wpi.edu / Pubs / ETD / Available / etd-051205-151955 / unrestricted / A.Hac quard.pdf Alexander Hacquard, Improving and Understanding DirectMethanol Fuel Cell (DMFC) Performance published in (paper submitted to Wo...

AI Technical Summary

Problems solved by technology

[0004] The most significant disadvantages of known fuel cells of the DMFC type are: too low power density due to slow electrochemical oxidation of methanol at the anode; and the ability of methanol to migrate across the PEM membrane (polymer electrolyte membrane) to the cathode where methanol is oxidized

This leads not only to fuel loss, but also to the carbon monoxide formed poisoning the platinum catalyst used at the cathode, which leads to reduced efficiency

The complexity of the reaction makes it difficult to obtain satisfactory yields

In addition, the membrane's ability to transport protons (hydronium ions) from the anode to the cathode is limited and easily exceeded, since each methanol molecule produces six protons that will pass through, which is compared to the two protons formed for each hydrogen molecule in the The situation is different in hydrogen fuel cells

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