When a chemical power source is in current generation mode its voltage decreases because of polarization, in particular because of concentration polarization, caused by electrodes electrolyte concentration change. It is possible to decrease the concentration polarization in oxyhydrogen flic! cells by means of water diffusion flow running through the electrolyte; in this case two types of electrochemical cells – the fuel cell itself and the concentration cell – operate jointly. Hydrogen humidification in cation-exchange membrane fuel cells allows both to prevent the membrane from drying and to increase the voltage through concentration loss reduction in electrolyte.