Development and testing of a PEM SO2-depolarized electrolyzer and an operating method that prevents sulfur accumulation

• Published in: International journal of hydrogen energy 2015-10, Vol.40 (39), p.13281-13294
• Main Authors: Steimke, John L., Steeper, Timothy J., Cólon-Mercado, Hector R., Gorensek, Maximilian B.
• Format: Article
• Language: English
• Subjects: 08 HYDROGEN; Electrolysis; Hybrid sulfur cycle; SO2-depolarized electrolysis; Sulfuric acid
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2015.08.041

The hybrid sulfur (HyS) cycle is being developed as a technology to generate hydrogen by splitting water, using heat and electrical power from a nuclear or solar power plant. A key component is the SO2-depolarized electrolysis (SDE) cell, which reacts SO2 and water to form hydrogen and sulfuric acid. SDE could also be used in once-through operation to consume SO2 and generate hydrogen and sulfuric acid for sale. A proton exchange membrane (PEM) SDE cell based on a PEM fuel cell design was fabricated and tested. Measured cell potential as a function of anolyte pressure and flow rate, sulfuric acid concentration, and cell temperature are presented for this cell. Sulfur accumulation was observed inside the cell, which could have been a serious impediment to further development. A method to prevent sulfur formation was subsequently developed. This was made possible by a testing facility that allowed unattended operation for extended periods. •A PEM SO2-depolarized electrolyzer was built and tested for the hybrid sulfur cycle.•37 different membrane electrode assemblies were tested.•Sulfur deposition was observed at the cathode in early testing.•The sulfur formation mechanism was identified and preventive measures developed.•Operation without sulfur deposition for over 200 h was successfully demonstrated.