Bismuth as a Desalination Electrode Material

Abstract

Addressing freshwater scarcity and the energy demands of desalination, capacitive deionization (CDI) offers an energy-efficient solution for brackish water treatment by applying low voltages (~1.2 V) to capture ions on charged electrodes. Conventional carbon-based CDI, however, is limited to low salt removal capacities (~15 mg/g). To enhance performance, hybrid-CDI with Faradaic electrodes, such as bismuth (Bi) nanopowders, is explored for high-capacity, cost-effective chloride capture, and possible desalination of the seawater. This study investigates two morphologically different Bi nanopowder electrodes in 0.1 M NaCl, revealing a sequential electrochemical mechanism - Bi to Bi₂O₃, BiOCl, and BiCl(OH)₂. Both samples exhibit near-reversible oxide formation, diffusion-controlled oxychloride production, and surface-confined hydroxylated oxychloride formation, though cathodic irreversibility poses challenges for complete film reduction. These findings highlight Bi electrodes’ potential for sustainable CDI desalination, with given morphology and purity offering significant advantages.