Fuel cell system

1. A fuel cell system comprising:

a fuel cell,

a fuel gas supplier configured to supply fuel gas to an anode of the fuel cell,

an oxidant gas supplier configured to supply oxidant gas to a cathode of the fuel cell,

an anode humidity sensor disposed at a fuel gas supply flow path;

a cathode humidity sensor disposed at an oxidant off-gas discharge flow path;

a humidity adjuster configured to adjust a relative humidity of the fuel gas and a relative humidity of the oxidant gas, and

a controller,

wherein the controller configured to detect the relative humidity of the fuel gas at an anode inlet of the fuel cell from the anode humidity sensor, and the controller detects the relative humidity of the oxidant gas at a cathode outlet of the fuel cell from the cathode humidity sensor, and

wherein, based on detection results, the controller controls the humidity adjuster so that the relative humidity of the fuel gas at the anode inlet is higher than the relative humidity of the oxidant gas at the cathode outlet;

wherein the humidity adjuster comprises a valve connected to a water supply, and wherein the humidity adjuster controls humidity by controlling an opening degree of the valve.

2. The fuel cell system according to claim 1 , wherein the relative humidity of the fuel gas at the anode inlet is 100% or more, and the relative humidity of the oxidant gas at the cathode outlet is 60% or less.

3. The fuel cell system according to claim 1 , wherein the relative humidity of the fuel gas at the anode inlet is 30% or more, and the relative humidity of the oxidant gas at the cathode outlet is 0% or more and less than 30%.