Isostructural Co/Ni-containing banana-shaped polyoxometalate for visible-light-driven hydrogen production

Abstract

Isostructural Ni/Co-containing banana-shaped polyoxometalate, (C2H8N)10[Ni3W2O2(OH)4(P2W15O55)2]·20H2O (Ni3P4) and (C2H8N)10[Co3W2O2(OH)4(P2W15O55)2]·26H2O (Co3P4), which exhibit novel structural features, were successfully synthesized through a one-pot hydrothermal method. The synthesized compounds were characterized by various techniques to determine their composition, crystal structure, and elemental oxidation states. Single-crystal X-ray diffraction confirms that the two isostructural compounds differ solely in the metal-oxo cluster cores: {Ni3W2} and {Co3W2}, respectively. The title complexs Ni3P4 and Co3P4 have been investigated as noble-metal-free catalysts for visible-light-driven hydrogen evolution in a three-component system. Under otherwise identical catalytic conditions, Ni3P4 displayed significantly enhanced hydrogen evolution catalytic activity relative to Co3P4, achieving a 6.5-fold higher catalytic efficiency. Comprehensive mechanistic studies reveal that the superior hydrogen evolution activity of Ni3P4 is not attributable to a more favorable photoinduced electron-transfer rate, but rather to the intrinsically higher proton reduction catalytic activity of the Ni center compared to Co.