Design and Fabrication of a Bismuth Nanowire Array as a Chloride-Storage Electrode for Desalination and Energy Storage Applications

Developing rechargeable seawater batteries with high storage capacity, cost-effectiveness, and lower energy consumption for desalination and energy storage is challenging. Bismuth (Bi) can be used as a storage electrode for chloride (Cl-) ions in rechargeable desalination batteries because neither Bi nor bismuth oxychloride (BiOCl) is soluble in a salt solution. In this study, we designed and fabricated bismuth nanowire (Bi NW) arrays as Cl--storage electrodes on two kinds of anodized aluminum oxide (AAO) prepared from phosphoric or oxalic acids, named P-AAO and O-AAO, respectively. Cl- can be effectively stored in the form of BiOCl in the Bi NW structure with a high aspect ratio. The morphology of honeycomb-shaped P-AAO and O-AAO templates used to grow the Bi NWs was analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) at desalination and salination. Also, the surface and structural morphology of the Bi sheet, P-AAO Bi NW arrays, and O-AAO Bi NW arrays before and after the adsorption/desorption of Cl- were examined. The half-cell reaction of the P-AAO Bi NW and O-AAO Bi NW arrays and thin Bi sheet array electrodes were subjected to linear sweep voltammetry (LSV) and cyclic voltammetry (CV) to study their chlorination/dechlorination behavior. The charge and discharge tests demonstrated that the structure of the Bi NW array was effective in facilitating the adsorption and desorption of Cl- ions. These results found that 88% of the P-AAO Bi NWs was electrochemically active during the oxidation and reduction process. This study can help open up an easy way to fabricate facile desalination and energy storage electrodes.