NiFeOH/CoP/NF composite electrode was fabricated by constructing a metal hydroxide layer on the surface of cobalt phosphide via hydrothermal, phosphating, and electrodeposition methods. The electrolytic water splitting to hydrogen performance by as-prepared electrode was investigated in 1.0 mol/L KOH medium. NiFeOH/CoP/NF composite electrode exhibited excellent water electrolysis performance, and the required overpotentials for HER and OER at 100 mA/cm² current density were 141 and 372 mV, respectively. When NiFeOH/CoP/NF electrode served as both cathode and anode for water splitting, only 1.61 V voltage was required to reach current density of 10 mA/cm². Because NiFeOH protection layer enhanced the electrocatalytic activity and stability of CoP for water splitting, NiFeOH/CoP/NF composite electrode exhibited high stability during the galvanostatic electrolysis in the HER and OER, and its activity could maintain 60000 s without significant performance degradation. The photovoltaic-electrolytic water cell constructed with two NiFeOH/CoP/NF electrodes and GaAs solar cell showed 18.0% efficiency of solar to hydrogen under 100 mW/cm² simulated solar irradiation and worked stably for 200 h.