Membrane electrode assembly and electrochemical hydrogen pump

A membrane electrode assembly comprising:

• an electrolyte membrane that includes a pair of main surfaces;
• a cathode catalyst layer that is provided to one main surface of the electrolyte membrane;
• an anode catalyst layer that is provided to the other main surface of the electrolyte membrane;
• a cathode gas diffusion layer that is provided to the cathode catalyst layer;
• and
• an anode gas diffusion layer that is provided to the anode catalyst layer,
• an anode gas diffusion device including:
• an anode main body that includes an anode gas diffusion layer that is provided to the anode catalyst layer;
• and
• an anode gas flow path plate, wherein
• the anode main body is provided between the anode gas flow path plate and the anode catalyst layer, wherein
• the anode gas diffusion layer includes a metal steel plate that includes a main surface and a plurality of vent holes through which gas passes, the main surface of the metal steel plate neighboring the anode catalyst layer,
• unevenness is provided to the main surface of the metal steel plate that neighbors the anode catalyst layer, and
• a difference in a height of the unevenness in a thickness direction of the metal steel plate is less than a thickness of the electrolyte membrane.