Efficient photocatalytic hydrogen production over ZnIn 2 S 4 by producing sulfur vacancies and coupling with nickel-based polyoxometalate.

A composite catalytic system using sulfur-vacancy-containing ZnIn 2 S 4 -Sv as a light-harvesting material and nickel-based polyoxometalate Na 6 K 4 [Ni 4 (H 2 O) 2 (PW 9 O 34 ) 2 ] (Ni4POM) as a co-catalyst was developed. The Ni4POM/ZnIn 2 S 4 -Sv composite gave a good hydrogen production rate of 337.5 μmol h -1 , a value 11.8 times higher than that of ZnIn 2 S 4 -Sv. The direction of electron transfer, from ZnIn 2 S 4 -Sv to Ni4POM, was verified using surface photovoltage spectra.