The effect of oxidation state of metal on electrochemical and photochemical driven hydrogen evolution catalyzed by nickel complexes of maleonitriledithiolate ligands

摘要

Two nickel-based catalysts, TBA(2)[Ni-II(mnt)(2)] 1 and TBA[Ni-III(mnt)(2)] 2 are formed by the reactions of NiCl2 center dot 6H(2)O, Na-2(mnt), and tetra-n-butylammoniumbromide (TBABr) without or with iodine (I-2) (mnt = 2,2-dicyanoethylene-1,1-dithiolate), respectively. Under an overpotential (OP) of 941.6 mV, complexes 1 and 2 can electrocatalyze hydrogen evolution from acetic acid with a turnover frequency (TOF) of 36.3 and 148.31 mol H-2/mol catalyst/h, respectively. Under blue light (lambda(max) = 469 nm), 1 or 2, together with CdS nanorods (CdS NRs) as a photosensitizer, and ascorbic acid (H(2)A) as a sacrificial electron donor, can produce hydrogen with a turnover number (TON) of 7760 and 17,570 moles of H-2 per mole of catalyst during 35 h irradiation, respectively. The average value of apparent quantum yield (AQY) is similar to 9.2% (complex 1) and 28% (complex 2), respectively. The results indicate that the nickel(III) complex has a better active activity for hydrogen production than the nickel(II) species.

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