Photoelectrochemical (PEC) water splitting is a promising approach to boost green hydrogen production. Herein, we prepared novel binder-free photoelectrode by direct growth of iron doped nickel oxide catalyst over activated carbon cloth (FexNi1-xO@a-CC) having band gap energy of 2.2 eV for overall water splitting. FexNi1-xO@a-CC photoelectrode had shown remarkable lower potential of only 1.36 V for oxygen evolution reaction (OER) to reach 10 mA cm−2 current density using very low photonic intensity of 8.36 × 10−4 E/L.s. For the first time, we also reported electrical efficiency required for PEC water splitting for 1 m3 of water that is equal to 0.09 kWh/m3. FexNi1-xO@a-CC photoelectrode also exhibits low potentials of 1.44 V (OER) and −0.210 V (HER) at 10 mA cm−2 to split sea water. Our results confirmed that designing FexNi1-xO@a-CC photoelectrode would be an innovative step to widen green energy conversion applications using natural waters (both sea and fresh water).