Electrochemical water-splitting in alkaline medium has gained massive attention for generating large-scale renewable hydrogen. Yet, it encounters challenges such as poor stability and high voltage at higher current density, particularly for insufficient electron transport kinetics. Therefore, the practical application of water electrolysis, a resilient electrocatalyst with superior efficiency and maximum metal utilization, is essential. In this research, a rational design of quadruple-phase interface-derived noble-metal-unbounded hierarchical 3D-interconnected multi-layered heterostructure CoCu-LDH@FeNi2S4–FeNiS2@CoNi2S4/NF as a self-sacrificed highly efficient electrode for affordable green H2 production through electrochemical water splitting in alkaline electrolyte is discussed. The resultant bifunctional electrode was synthesized through a controllable two-step hydrothermal approach. The hybrid electrocatalyst exhibited outstanding electrocatalytic performance towards oxygen evolution reaction (η10 ∼240 mV) and hydrogen evolution reaction (η10 ∼87 mV) to achieve a current density of 10 mA cm−2 with long-term stability. Impressively, the alkaline water electrolyzer delivered a cell voltage of 1.56 V@10 mA cm−2 and remarkable stability due to the significant synergistic interfacial effect among the different phases, high electrical conductivity, rich exposed active sites with optimized free energy of chemisorbed reaction intermediates, high intrinsic activity, and numerous open channels for ion diffusion with mass transport at the interface. This research strategy provided insight into designing non-noble transition metal-based electrocatalysts by engineering interfacial active sites toward industrial-scale green hydrogen production.