Two-dimensional ultrathin ZnxCd1-xS nanosheet was fabricated by topotactic sulfurization process using trimetallic ZnCdAl layered double hydroxides (LDHs) as precursor and thiourea as sulfur source. A series of characterizations were conducted to investigate the structure and properties of ZnxCd1-xS nanosheet. The band gap engineering of ZnxCd1-xS nanosheet can be tuned by the composition of LDH precursor, keeping balance between photo-absorption ability and flat band potential. ZnxCd1-xS nanosheet possessed exposed (111)ZB or (002)WZ polar facet. Zn0.67Cd0.33S nanosheet displayed not only the highest photocatalytic hydrogen-generation activity under visible light irradiation (6.69 mmol h(-1)g(-1)) without cocatalyst, but also outstanding stability after several cycles. In spite of the poor surface area of the nanosheet, it can be concluded that the carrier separation and transport rate of ZnxCd1-xS nanosheet significantly enhanced, rendering photogenerated carriers transport across the polar facet. This can be attributed to the photogenerated electron/hole exclusively delocalized distributed on the metal/sulfur ions, respectively. This work presents a strategy to fabricate highly efficient ZnxCd1-xS nanosheet from LDH precursor, which is a simple, low-cost and environmentally friendly process. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.