Electrocatalytic water splitting using bi-functional catalysts is one of the most promising approaches for clean hydrogen fuel production. To address shortcomings of the existing catalysts, here we develop a new bi-functional catalysts cobalt-based nano-architecture with ordered, Ni-doped two-dimensional (2D) defect-rich nanosheets. Innovative combination of doping, annealing, and sulfidation is developed to fabricate the hierarchical porous metal sulfide (denoted as Ni-Co-S) nanosheets arrays (HPNA) directly on conductive carbon cloth (CC). Owing to the unique architecture with the specific surface area and porous structure, short ion diffusion paths, the Ni-Co-S HPNA exhibits excellent electrocatalytic activitiy for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline solution, featuring low overpotentials of 110 and 270 mV at a current density of 10 mA cm−2, respectively. The excellent catalytic performance is attributed to the unique porous structure, abundant active sites and efficient mass transport. More importantly, when the Ni-Co-S HPNA serves as both the anode and cathode, it achieves a 1.62 V at 10 mA cm−2 and remains stable over 12 h of the overall water splitting process. This work opens new avenues for rational design of high-efficiency and stable bifunctional electrocatalysts for water electrolysis and a broader range of clean energy and sustainable chemistry applications.