Facile and Reproducible Electrochemical Synthesis of the Giant Polyoxomolybdates

Giant polyoxomolybdates are traditionally synthesized by chemical reduction of molybdate in aqueous solutions, generating complex nanostructures such as the highly symmetrical spherical {Mo₁₀₂} and {Mo₁₃₂}, ring-shaped {Mo₁₅₄} and {Mo₁₇₆}, and the gigantic protein sized {Mo₃₆₈}, which combines both positive and negative curvature. These complex polyoxometalates are known to be highly sensitive to reaction conditions and are often difficult to reproduce, especially {Mo₃₆₈}, which is often produced in yields far below 1%, meaning further investigation has always been limited. While the electrochemical properties of these materials have been studied, their electrochemical synthesis has not been explored. Herein, we demonstrate an alternative reliable synthetic method by means of electrochemistry. By using electrochemical synthesis, we have shown the synthesis of various reported polyoxomolybdates, along with some unreported structures with unique features that have yet to be reported by traditional synthetic methods. The six different giant polyoxomolybdates that were obtained via electrochemical synthesis range from the spherical {Mo_102-Fe} and {Mo₁₃₂} to the ring-shaped {Mo₁₄₈} and {Mo_154-}, as well as the largest known polyoxometalate {Mo₃₆₈}, with improved yield (up to 26.1% for {Mo₃₆₈}), increased reproducibility, and shorter crystallization time compared to chemical reduction methods.