In this study, a novel heterojunction of nickel cobalt selenide with metal phase molybdenum selenide nano spheres was synthesized via a facile hydrothermal method and assembled with a solar cell for dual-functional water splitting. The resulting nanospheres, composed of nickel cobalt selenide and molybdenum selenide (NCSMS), display low overpotentials of 290 and 370 mV for the oxygen evolution reaction at 50 and 100 mA cm − 2 , and 244 and 304 mV for the hydrogen evolution reaction at 50 and 100 mA cm − 2 , respectively, in 1.0 M potassium hydroxide. In addition, the overpotential required during urea electrolysis is also low, at 170 and 260 mV at 50 and 100 mA cm − 2 in 1.0 M potassium hydroxide and 0.33 M urea electrolyte. The NCSMS-based electrolyzer requires only 1.5 V of operating power at 10 mA cm − 2 , and when NCSMS catalysts are used in the MEA, a current density of 408 mA cm − 2 at 1.85 V can be achieved with 69.13% cell efficiency. Experimental and computational data both confirm that NCSMS is an excellent dual-functional electrocatalyst for electro chemical water splitting to produce hydrogen. Moreover, the scientists have successfully fabricated and tested a wireless assembly of NCSMS with a solar cell for overall water splitting, which further demonstrates the potential of NCSMS to contribute to efficient green energy production.