The nano-on-micro heterostructure photocatalyst BiOI-MoS2/CdS was synthesized through facile in-situ hydrothermal and solvothermal growth methods. The heterostructures formed between BiOI, MoS2 and CdS realized a step-wise electron transfer process, thus reducing the charge recombination effectively. The light absorption range of the composite was expanded with the incorporation of BiOI. The specimen acts out a state-of-the-art hydrogen evolution of 14000 mu mol/g/h under visible light (lambda > 420 nm), which was far exceeding MoS2/CdS (460 mu mol/g/h) by a factor of 30. BiOI is firstly applied to promote photocatalytic water splitting into hydrogen. What's more, the cost of photocatalytic water splitting into hydrogen will be greatly reduced by replacing noble metal cocatalyst with MoS2. The opportunities for developing low-cost efficient photocatalysts for water splitting may be opened because of this discovery. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.