It is widely acknowledged that interface engineering strategies can significantly enhance the activity of catalysts. In this study, we developed a CoMoP nanoarray directly grown in situ on a nickel foam (NF) substrate, with the interface structure formed through the electrodeposition of MnOxHy. The resulting heterostructure MnOxHy/CoMoP/NF exhibited remarkable hydrogen evolution reaction (HER) activity, achieving overpotentials as low as 61 and 138 mV at 10 and 100 mA cm-2, respectively. Moreover, MnOxHy/CoMoP/NF demonstrated efficient oxygen evolution reaction (OER) activity with an overpotential of 330 mV at 100 mA cm-2. Remarkably, MnOxHy/CoMoP/NF maintained its catalytic properties and structural integrity even after working continuously for 20 h facilitating the HER at 10 mA cm-2 and the OER at 100 mA cm-2. The Tafel slopes of the HER and OER were determined to be as small as 14 and 55 mV dec-1, respectively, confirming that the coupled interface conferred fast reaction kinetics on the catalyst. When applied in overall water splitting, MnOxHy/CoMoP/NF delivered a voltage of 1.91 V at 100 mA cm-2 with excellent stability. This study demonstrated the feasibility of utilizing a simple electrodeposition technique to fabricate a heterogeneous structure with bifunctional catalytic activity, establishing a solid foundation for diverse industrial applications.