Method for operating a fuel cell

A method for operating a fuel cell comprising

• (i) a proton-conducting polymer electrolyte membrane or polymer electrolyte matrix,
• (ii) at least one catalyst layer which is arranged on both sides of the proton-conducting polymer electrolyte membrane or polymer electrolyte matrix,
• (iii) at least one electrically conductive gas diffusion layer which is arranged on both averted sides of the catalyst layer,
• (iv) at least one bipolar plate which is arranged on both averted sides of the gas diffusion layer,
• comprising the following steps:
• a) supplying a hydrogen-containing gas through the gas diffusion layer to the catalyst layer on the anode side by means of the gas ducts present in the bipolar plate,
• b) supplying a gas mixture containing oxygen and nitrogen through the gas diffusion layer to the catalyst layer on the cathode side by means of the gas ducts present in the bipolar plate,
• c) generating protons at the catalyst layer on the anode side,
• d) diffusing the generated protons through the proton-conducting polymer electrolyte membrane or polymer electrolyte matrix,
• e) reacting the protons with the oxygen-containing gas supplied from the cathode side,
• f) tapping the formed voltage potential by means of the bipolar plate on the anode side and on the cathode side,
• wherein, to switch off the fuel cell, the supply of the gas mixture which contains oxygen and nitrogen is discontinued and the oxygen present at the cathode is reacted to exhaustion by means of reaction with the protons present and the residual oxygen content at the cathode side of the fuel cell is reduced to a concentration of 5% by volume and less.