FUEL CELL, FUEL CELL SYSTEM, AND OPERATING METHOD FOR A FUEL CELL

A fuel cell of the present invention includes cell blocks (101, 102) each formed by stacking cells (51, 52) and a cooling medium connecting channel (103) connecting a cell block internal cooling medium channel (153A) of the cell block (101) and a cell block internal cooling medium channel (153B) of the cell block (102) in series. A catalyst layer includes a catalyst support and polymer electrolyte adhered to the catalyst support, the catalyst support containing an electrode catalyst and carbon powder supporting the electrode catalyst. The catalyst layer in the cell 52 of the cell block (102) located downstream of the cooling medium connecting channel (103) is higher or larger in at least one selected from the group consisting of a density of an ion exchange group per unit volume of the catalyst layer, an electrode catalyst supporting amount of the catalyst support of the catalyst layer, and a catalyst supporting rate of the catalyst layer, than the catalyst layer of the cell 51 of the cell block 101 located upstream of the cooling medium connecting channel 103.