Entropy analysis of hydrogen production in electrolytic processes

Hydrogen-based energy has great potential for modernizing current and future heat and electricity generation structures and for decarbonizing industrial technologies. Hydrogen production is one of the basic areas in which technical and economic solutions must be found. The first part of the work presents general information on the production of hydrogen from fossil fuels and by using water decomposition methods. The main purpose of the article is thermodynamic analysis of two types of polymer and oxide electrolysers. The analysis is carried out using the entropy method. The standard potential and the algorithm for determining the current-voltage characteristics of the electrolyser are defined. The energy and entropy balance is recorded for the selected electrolyser module configuration. Entropy generation values corresponding to activation, ohmic and concentration losses are calculated for selected temperature and current density values. The results of the calculations make it possible to compare the intensity of the losses for the two considered types of electrolysers depending on changes in their operating parameters. Using the results of parametric entropy calculations, the heat generated during electrolysis is determined. Due to that, it is possible to establish the regions of endo- and exothermic work of both classes of cells. These are important data for the construction of electrolyser stacks and their integration with power sources. The thermodynamic efficiency of electrolysis is defined and discussed. A new indicator is proposed for assessing the quality of electrochemical processes occurring in the analysed types of electrolysers (relation 47). As demonstrated by the calculation results (cf. Figs. 10 and 11), the value of the indicator is significantly affected by temperature and current density. Areas of variability of parameters for which there is a potential for improving thermodynamic efficiency are indicated for both types of the electrolysers under consideration.