LAUSR

P‐type Ni(OH)2 has been combined with n‐type CdS nanorods and nanocrystals for enhanced photocatalytic property due to the p‐n junction. Though CdS nanosheets exhibit fast charge transfer and large superficial area, the decoration of Ni(OH)2 was rarely reported up to now. In this work, the photo‐deposition of Ni(OH)2 nanoparticles on CdS ultrathin nanoflakes was established for efficient photocatalytic H2 generation. By changing the irradiation time of CdS, the reaction between Ni2+ and OH− can be controlled for different loading density of Ni(OH)2. As the loading density‐dependent morphology, light absorption, carrier separation and transfer were systematically studied for the composites, an obvious band gap narrowing from 2.28 to 2.08 eV was revealed, and the carrier separation and transfer between the CdS nanoflakes and Ni(OH)2 nanoparticles have been enhanced for the composites with deposition time of 3 minutes. These together with the alignment of type “II” bands and the high specific surface area of the flakes and nanoparticles, lead to an optimum H2 generation of 20.14 mmol/g/h, nearly three times of pure CdS (7.97 mmol/g/h). Such a study not only provides a deposition method of Ni(OH)2, but also sheds light on the enhancement strategy for photocatalytic property by controlling the microstructure and aligning the hetero‐structured bands.