Thermodynamic and electrochemical assessment of an alkaline electrolyzer (AE) at different operating parameters

In the study, the alkaline electrolyzer is thermodynamically and electrochemically analyzed under various operating parameters for optimum hydrogen production. The effects of varying operating parameters such as temperature, current density, exchange current density for anode and cathode, and the thickness of the electrolyte on the cell potential is investigated. Moreover, the overall performance of the electrolyzer is investigated through energy and exergy analysis. This study is demonstrated the electrochemical characteristics that are attached to the thermodynamic analysis of the electrolyzer. The current density-cell voltage (i-V) characteristic curve is a unique feature of its design which is generated at different operating parameters. Further, this curve for different losses such as ohmic and activation overpotentials are generated. The results show that the activation overpotential dominates the total voltage loss; the electrodes of the electrolyzer are more active at higher working temperatures leading to a lower activation overpotential; the cell potential decreases considerably with increasing i0 and increases significantly with an increase in electrolyte thickness due to higher ohmic overpotential; the electrolyzer works in an exothermic mode since the heat generation exceeds the thermal energy requirement because of the overpotentials. The experimental data existing in the literature are also compared with the current density-cell voltage (i-V) curve in the study that showed high similarity. The energy and exergy efficiency based on the H2 yield governed by the electrical energy input alone is almost the same (55-56%) since electricity has 100% exergy.

Automated summary

This study investigates the optimal hydrogen production of an alkaline electrolyzer under various operating parameters through thermodynamic and electrochemical analysis. It reveals that activation overpotential is the main source of voltage loss, electrodes are more active at higher working temperatures, and an increase in electrolyte thickness leads to higher ohmic overpotential.