Composite electrode for use in electrochemical cells

An electrochemical cell comprising:

• current collector means for conducting electrons generated by electrochemical reactions of fuel within said electrochemical cell;
• ion conductor means for selectively conducting preselected ions liberated by said electrical reactions;
• and
• a composite electrode positioned between said collector means and said ion conductor means, said composite electrode having varying ion and electron transport rates therethrough and having an electrocatalyst positioned within a zone in the section of said electrode wherein said rates are substantially equal.

A porous composite electrode for use in an electrochemical cell having a first face and a second face defining a section therebetween, said composite electrode comprising:

• ion conductor means defining an ion transport rate through said electrode, said electrode having a volume concentration of said ion conductor means which is the greatest at said first face and which is decreased across said section;
• electron conductor means defining an electron transport rate through said electrode, said electrode having a volume concentration of said electron conductor means which is the greatest at said second face and which is decreased across said section;
• and
• an electrocatalyst positioned within said section in a relatively narrow zone where the rate of electron transport is approximately equal to the rate of ion transport.

A porous composite electrode for use in an electrochemical cell comprising:

• a first zone for conducting both electrons and ions liberated by electrochemical reactions in said electrochemical cell, the rate at which said first zone transports said electrons being greater than the rate at which said first zone transports ions;
• a second zone for conducting both electrons and ions liberated by said electrochemical reactions, the rate at which said second zone transports said ions being greater than the rate at which said second zone transports electrons;
• a third zone contiguous with said first and said second zones and having an ion transport rate and an electron transport rate which are approximately equal;
• and
• an electrocatalyst for increasing the rate of said electrochemical reactions, substantially all of said electrocatalyst being positioned within said third zone.