An electrochemical cell stack is provided. The electrochemical cell stack has a plurality of electrochemical cells. Each electrochemical cell has a membrane electrode assembly which includes a cathode catalyst layer, an anode catalyst layer, and a polymer membrane interposed between the catalyst layer and the anode layer. Each electrochemical cell also has an anode plate and a cathode plate with the membrane electrode assembly interposed therebetween, and a cathode flow field positioned between the cathode plate and the cathode catalyst layer. The cathode flow field includes a porous structure having a plurality of pores having an average pore size. The plurality of electrochemical cells has a first electrochemical cell positioned at a first end of the electrochemical cell stack. The porous structure of the first electrochemical cell has an average pore size greater than the average pore size of the porous structures of the plurality of electrochemical cells. And, the porous structure of the first electrochemical cell has a flow resistance less than an average flow resistance of the porous structures of the plurality of electrochemical cells.