The nanoflowers copper-zinc oxide (CZO) heterostructure has been prepared using the hydrothermal method. As it exhibits a low band gap energy the material may absorb large amounts of natural sunlight. Under visible light irradiation, CZO showed signs of activity towards hydrogen production in the two conditions, which are: i) the condition of photocatalytic reaction with light as the only energy source, in the presence of a sacrificial electron donor and; ii) the photo-electrochemical conditions when the material was deposited onto biased conductive support, in pure water. The improved activity and stability of CZO results from a mutual charge transfer between copper oxide and zinc oxide. Therefore we can suggest that under illumination photogenerated electrons from the conduction band of copper oxide migrate to conduction band of zinc oxide, while holes migrate in the opposite direction, thus improving the charge separation and lowering the rate of unfavourable recombination. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.