Water electrolysis apparatus

A water electrolysis apparatus that performs water electrolysis in which hydrogen and oxygen are obtained by supplying water to water electrolysis cells and applying voltage to the water electrolysis cells,

• the water electrolysis apparatus comprising:
• a water electrolysis stack in which the water electrolysis cells are stacked;
• a water supply side path through which water is supplied to the water electrolysis stack;
• a hydrogen side path through which hydrogen generated from the water electrolysis stack is collected;
• an electric power source that applies the voltage to the water electrolysis stack;
• and
• a controller that controls application voltage of the electric power source, wherein at times of startup and stop of the water electrolysis apparatus, the controller controls
• the electric power source such that an average change rate of a current density is higher in a region where the current density is equal to or lower than 0.4 A/cm2 than in a region where the current density is higher than 0.4 A/cm2 and is equal to or lower than a current density at a time of steady operation of the water electrolysis apparatus.

A water electrolysis apparatus that performs water electrolysis in which hydrogen and oxygen are obtained by supplying water to water electrolysis cells and applying voltage to the water electrolysis cells,

• the water electrolysis apparatus comprising:
• a water electrolysis stack in which the water electrolysis cells are stacked;
• a water supply side path through which water is supplied to the water electrolysis stack;
• a hydrogen side path through which hydrogen generated from the water electrolysis stack is collected;
• an electric power source that applies the voltage to the water electrolysis stack;
• and
• a controller that controls application voltage of the electric power source,
• wherein the controller controls the electric power source such that a current density reaches 0.4 A/cm2 within 5 seconds at a time of startup of the water electrolysis apparatus and the water electrolysis apparatus reaches a stopped state within 5 seconds after the current density reaches 0.4 A/cm2 at a time of stop of the water electrolysis apparatus.