Electrochemical production of hydrogen in molten salt

• Electrochemical behavior of protons dissolved in molten salt. • Reduction of dissolved protons is a diffusion-controlled process. • Catholic polarization is influenced by the level of moisture. • Hydrogen production with a Faradaic efficiency of 83% at 1.5 V. Clean and economical production of hydrogen is a key step for the decarbonization of energy systems. Current water electrolysis technologies developed for the green hydrogen production require high voltage values of around 2.0 V, making them uneconomical for large-scale applications. The voltage required for the production of hydrogen can be substantially reduced to around 1.0 V by performing the electrolysis at high temperatures. This article concerns the low-cost and green electrolytic production of hydrogen operating at such a low voltage performed by the dissolution of steam in high temperature molten salt electrolytes, and the subsequent electrochemical reduction of the dissolved hydrogen ions. The electro-generation of hydrogen is confirmed by performing cyclic voltammetry using molten lithium chloride as the electrolyte at 660 °C under a flow of moisturized argon. Furthermore, hydrogen is generated by the electrolysis of molten salt containing hydrogen ions using a nickel foam cathode at the constant cell voltage of 1.5 V with a high Faradaic efficiency of 83.2%. The results obtained provide crucial insights for further development of molten salt technologies for clean and efficient hydrogen production.