A structurally-new, carbon-free hexadecanuclear Ni-containing silicotungstate, [Ni16(H2O)15(OH)9(PO4)4(SiW9O34)3]19-, has been facilely synthesized using a one-pot, solution-based synthetic method systematically characterized by single-crystal X-ray diffraction and several other techniques. The resulting complex works as a noble-metal-free catalyst for visible-light-driven catalytic generation of hydrogen, by coupling with a [Ir(coumarin)2(dtbbpy)][PF6] photosensitizer and a triethanolamine (TEOA) sacrificial electron donor. Under minimally optimized conditions, a turnover number (TON) of 842 was achieved for TBA-Ni16P4(SiW9)3-catalyzed hydrogen evolution system. The structural stability of TBA-Ni16P4(SiW9)3 catalyst under photocatalytic conditions was evaluated by the mercury-poisoning test, FT-IR, and DLS measurements. The photocatalytic mechanism was elucidated by both time-solved luminescence decay and static emission quenching measurements.
Keywords: Ni substitution; hydrogen production; photocatalysis; polyoxometalates.