An activation method and system to selectively activate defective cells in a laminated fuel cell stack. The system includes a tank to store a polar solvent used to activate the cells; a body including a transfer unit to transfer the polar solvent to the fuel cell stack and a control unit to control the transfer unit; and a nozzle coupled to the body, to be inserted into an inlet manifold of the fuel cell stack. The nozzle has an opening positioned opposite to a channel inlet of at least one non-activated cell of the plurality of cells, to jet the polar solvent into only a channel of the non-activated cell, through the opening.