Patent ID: 8227124

Claim:
A method of controlling reactions in a fuel cell, comprising: providing a membrane electrode assembly comprising a proton exchange membrane sandwiched between a pair of electrodes, at least one of the electrodes having an active area comprising a variable catalyst loading; and providing an electrically conductive fluid distribution element having a flow field defined by channels facing at least one electrode; determining the variable catalyst loading by measuring temperature distribution of the at least one electrode with a uniform catalyst loading using an array of temperature-sensing resistors to detect an area or areas of increased temperature, then decreasing catalyst loading in the detected area or areas to provide a variable catalyst loading, wherein the variable catalyst loading provides localized control of a non-uniform reaction rate in respective regions faced by said flow field, wherein certain ones of said regions faced by said electrically conductive fluid distribution element are cooled- and said variable catalyst loading is varied according to the non-uniform reaction rate and the extent of cooling.