Tetrabutylphosphonium hexafluorophosphate is primarily used as an ionic liquid in various electrochemical applications. Its high thermal stability and conductivity make it suitable for use in batteries, supercapacitors, and fuel cells, where it acts as an electrolyte to facilitate ion transport. Additionally, it is employed in organic synthesis as a phase-transfer catalyst, enhancing reaction rates and selectivity in processes such as nucleophilic substitutions and polymerizations. Its non-volatile nature and ability to dissolve a wide range of materials also make it useful in green chemistry, reducing the need for harmful solvents. Furthermore, it is utilized in the preparation of advanced materials, including nanoparticles and coatings, due to its unique physicochemical properties.