Ballard Power Systems Corporation

National Research Council of Canada

Sfc Smart Fuel Cell Ag

Jiujun Zhang

Kevin M Colbow

David P Wilkinson

Jens M&uuml;ller

Peter Urban

Regina Wezel

Joy A Roberts

Jean St-Pierre

Cindy J Longley

Marian E Van Der Geest

Jens Müller

Alfred Wong

Gustav A Boehm

Jun Shen

Haijiang Wang

Bruce Lin

Caikang (Elton) Gu

Monica Manmohan Kaila

The invention described relates to an apparatus and method for measuring the concentration of a low molecular weight alcohol, in an aqueous liquid feed solution, comprising a first sensor including a hydrophilic capillary tube having an inner diameter, being disposed between two electrodes to form a first capacitor, a second sensor including a hydrophobic capillary tube having the same inner diameter as a capillary tube of the first sensor; said hydrophobic capillary tube having a hydrophobic coating on the inner diameter, being disposed between two electrodes to form a second capacitor, wherein the first hydrophilic and second hydrophobic sensors are dipped to the same depth in the aqueous solution to measure the solution concentration, means for measuring the capacitance of the two capacitors, and control means including a control circuit driven by a computer, wherein the difference in capacitance between the two capacitors is a measure of the concentration of the solution, independent of the depth of dipping of the two capacitors in the aqueous solution. In another embodiment, a single hydrophilic sensor is employed.

Sensor for measuring the concentration of a solvent or solute in a mixed solution system

The performance of a direct feed fuel cell such as, for example, a direct methanol fuel cell, with an anode having a CO-tolerant catalyst, such as a Pt&#x2014;Ru catalyst, is improved by periodically reducing the output power of the cell to be less than the normal minimum output of the cell. This is effected, for example, by switching the cell at predetermined time intervals to an open circuit or reduced output power condition.

Method of improving the performance of a direct feed fuel cell

Fuel cells are disclosed that operate directly on fuel streams comprising tetramethyl orthocarbonate in which tetramethyl orthocarbonate is directly oxidized at the anode and, more particularly, to solid polymer fuel cells operating directly on liquid fuel streams comprising tetramethyl orthocarbonate. Also disclosed are methods relating thereto.

Tetramethyl orthocarbonate fuel cells and systems and methods related thereto

Low temperature fuel cells, e.g. solid polymer fuel cells, can operate directly on a fuel comprising dimethyl ether with dimethyl ether being oxidized at the fuel cell anode. Being highly soluble in water, dimethyl ether can be supplied as a liquid aqueous fuel solution. As a fuel, dimethyl ether provides similar power characteristics as methanol but typically with a greater Faradaic efficiency in liquid feed solid polymer fuel cells.

Direct dimethyl ether fuel cells

In an operating liquid feed fuel cell system, fuel concentration in the fuel stream can be calculated as a function of the observed current, the temperature of the fuel stream entering the fuel cell stack, and the temperature of the fuel cell stack itself, thereby eliminating the need for a separate sensor. Typically, methanol will be used as the fuel and the liquid feed fuel cell system will thus be a direct methanol fuel cell system.

Indirect measurement of fuel concentration in a liquid feed fuel cell

The measuring range of a fuel cell based concentration sensor can be extended by decreasing the load across the fuel cell terminals and by increasing the amount of oxidant supplied to the fuel cell. In this way, such a sensor avoids saturation, for example, when measuring methanol concentrations from 0 M to over 4 M in liquid aqueous solution. Such a sensor is suitable for use in measuring fuel concentrations in the recirculating fuel stream of certain fuel cell stacks (for example, direct methanol fuel cell stacks).

Fuel cell concentration sensor

An electrochemical fuel cell is operated with periodic reactant starvation at either or both electrodes. Periodic reactant starvation conditions cause a change in the potential of the starved electrode and may result in the removal of electrocatalyst poisons and in improved fuel cell performance. This technique may have other beneficial effects at the electrodes, including performance improvements due to water management effects or localized heating effects at the starved electrode. In a preferred method, while successive localized portions of a fuel cell electrode are periodically reactant starved, the remainder of the fuel cell electrode remains electrochemically active and saturated with reactant such that the fuel cell is able to continue to generate power.

Method and apparatus for operating an electrochemical fuel cell with periodic reactant starvation

Liquid feed fuel cell performance can be increased by impregnating electrode substrates with a proton conducting ionomer prior to incorporation of the electrocatalyst, and optionally also after application of the electrocatalyst. Ionomer impregnation is particularly effective for direct methanol fuel cell anodes that comprise carbonaceous substrates.

Ionomer impregnation of electrode substrates for improved fuel cell performance

Fuel cell performance in liquid feed fuel cells with an electrode comprising a carbonaceous substrate and an electrocatalyst can be increased by oxidizing the carbon substrate, particularly by electrochemical methods in acidic aqueous solution, prior to incorporation of the electrocatalyst. The treated substrate may thereafter be advantageously impregnated with a proton conducting ionomer to prevent excessive penetration of the applied catalyst into the substrate. The treatment method is particularly effective for direct methanol fuel cell anodes.

Growing community of inventors

Richmond, CA, United States of America

Jiujun Zhang