Validation and Mechanism of a Low-Cost Graphite Carbon Electrode for Electrochemical Brine Valorization
Linchao Mu, Yichong Wang, William A. Tarpeh
Abstract
Desalination adoption outpaces the development of effective strategies for managing the concentrated brine streams it produces. Electrochemical water-salt splitting to generate useful chemicals is an ideal method to valorize wastewater from desalination and incentivize its collection, which can expand the adoption of desalination to inland regions. We designed a three-chamber electrochemical cell that splits brine to generate an acid (HCl) and a base (NaOH). The three chambers were separated by an anion exchange membrane (AEM) and a cation exchange membrane (CEM), and the reactor operated robustly in various realistic brine concentrations (13,000–35,000 ppm NaCl). Buffer species, including carbonate, borate, and phosphate, reduced proton leakage through the AEM and did not introduce other side reactions. By testing several anodes for stability and selectivity toward oxygen evolution, we found that graphite carbon exhibited a 25% higher acid generation than mixed-metal oxides (Ti–Ir and Ti–Pt) and a 69% selectivity toward oxygen evolution because of a lower chloride adsorption on its surface (44% less chloride oxidized). This study advances material development, reactor design, and mechanistic understanding for electrochemical salt-water splitting to produce commodity chemicals from desalination brine.