Alternative thermochemical cycles are promising technologies for producing hydrogen by taking advantage of the waste heat from nuclear reactors. These cycles, which consist of two or more interrelated chemical reactions and are typically realized at moderately elevated temperatures (500-750 °C), are still at early stages of research, and more information is needed to evaluate their potential. The first proof-of-principle studies were performed for the electrolysis reaction of the K-Bi thermochemical cycle. Experiments were carried out in a ceramic reactor at 580 °C, and the experimentally measured electrolysis potentials were found to be close to the theoretically estimated values. This suggests that the voltage efficiency of the reaction can be as high as 90%.