Designing durable and highly active photoelectrocatalysts for overall water splitting is very challenging. Here, we report an easy method for synthesizing a highly efficient three-dimensional core-shell photoelectrocatalyst. This catalyst consists of cadmium sulfide as the core and nickel-cobalt layered double hydroxide as the shell, thus CdS@NiCo-LDH. The advantages of this catalyst are high specific surface area, rapid transfer of electrons, and open channels for the release of gaseous products, which lead to better oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline environments. The use of this catalyst in water decomposition for OER allows current density values of 10, 100, 500, and 1000 mA cm(-2) at a voltage of 132, 198, 306, and 309 mV, respectively. Also, using this catalyst for HER allows current density values of 10 and 100 mA cm(-2) at a voltage of 379 and 202 mV respectively.