Improvement of the membrane-free electrolysis process of hydrogen and oxygen production

Abstract

Renewable energy sources provide an unstable energy flow to the units of an autonomous energy complex. Therefore, in order to use the electrolyzer as an element of the considered complex, it is necessary to determine the optimal range of changes in the current density and evaluate the effect of operating characteristics of the electrolysis process on the evolution of H2 (O2) when the electrolyzer power supply is disconnected for 13 seconds against the background of a continuous base current level. Purpose. The main purpose of the research is to determine the rational range of changes in the current density supplied to a monopolar membrane-free high-pressure electrolyzer, as well as to determine the effect of a discrete current supply on electrochemical reactions during electrolysis. Methodology. Comprehensive studies on the electrochemical processes of water decomposition in alkaline electrolyte with the formation of hydrogen and oxygen in an experimental construction make it possible to cyclically supply power to the electrolyzer with visual control of the considered processes. Findings. The technology of cyclic generation of hydrogen and oxygen, which eliminates the need to use separating ion-exchange membranes, is considered. A rational range of changes in the current density on a membrane-free monopolar high-pressure electrolyzer with the usage of electrodes made of metals with variable valence is established. The influence of the discrete supply of electrical energy to the electrolysis cell is determined depending on the electrochemical reactions occurring on the active iron electrode. Theoretical values of the voltage of the oxidation and reduction of the iron electrode active mass, as well as the voltage on the half-cycle of hydrogen evolution during the electrolysis of water, are calculated. Originality. An increase in the blackout time from 1 to 3 s leads to a corresponding increase in time of the oxidation process on the hydrogen half-cycle by a factor of 2.4. In addition, the total amount of hydrogen (oxygen) released during the corresponding half-cycles remains unchanged and amounts to Practical value. The optimal range of current density for the operation of a membrane-free high-pressure electrolyzer is in the range of 200400 A/m2. Under such conditions, an intense redox process of the iron electrode active mass occurs. Electrical energy consumption in this case is in the range of 3.94.1 kW h/m3. An experimental study on the electrolyzer discrete power supply effect on its ability to generate gas is carried out. This makes it possible to supply electrical energy to the electrolysis cell directly from the primary energy source (sun, wind) as part of the energy technology complex.