Shokhrukhbek Bakhramov, Astan Ismailov
This study provides the inaugural comprehensive assessment of an ultra-low current density (3 mA/cm²) portable alkaline electrolyzer utilizing uncoated SS316L electrodes, illustrating the essential trade-offs among simplicity, cost (<$800), and efficiency in off-grid hydrogen production. The system has an energy efficiency of 9.6%, which shows that it loses voltage in three ways, 45% from the oxygen evolution reaction (OER) kinetics on bare steel, 25% from 2 mm electrode gaps, and 20% from room-temperature operation. The device runs on 13 V and 7.8 A (101 W) from a solar panel and produces hydrogen at a rate of 0.054 L/min (STP) with an energy cost of 350 kWh/kg H₂. Three experimental runs verified repeatability with a 5% margin of error. Dynamic testing with different power inputs (50 to 100 W) kept Faradaic efficiency above 95%, which showed that the system was compatible with solar energy. Quantitative loss investigation using electrochemical impedance spectroscopy found that OER overpotential (0.45 V) and ohmic losses (0.35 V) were the main problems. The results present benchmarked performance metrics for low-cost, portable green hydrogen systems and clarify how to improve performance, zero-gap architecture could lower cell voltage by 0.3 V, and NiFe catalyst coatings could reduce OER overpotential by 0.2 V, which could increase overall efficiency to about 20%.