Analysis of sodium generation by sodium oxide decomposition on corrosion resistance materials: a new approach towards sodium redox water-splitting cycle

Abstract

In this study, the investigation of materials with corrosion resistance was carried out to prevent side reactions caused by sodium oxide (Na₂O) in the Na-redox thermochemical water splitting cycle, and essential operational conditions for sodium (Na) generation from Na₂O were also investigated. Thermal desorption spectroscopy and X-ray diffraction techniques at altered conditions were mainly used for the experimental investigation. Numerous types of materials were tested to find materials with high resistance towards corrosion and to understand essential thermal decomposition processes of Na₂O. In addition, under different temperatures and pressure conditions, the thermodynamic calculation of Gibbs free energy was performed to obtain experimental results. As a result, a Ti alloy showed significant resistance towards the corrosive reaction by Na₂O. The obtained experimental and simulated results support the direct decomposition of Na₂O to form Na and O₂ below 600 °C under low partial pressure conditions. The optimized conditions for Na generation with the Ti alloy sample can be used for low temperature water splitting.