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• A universal strategy to synthesize amorphous/crystalline PMo-CoNiS heterostructures. • The dual doped PMo-CoNiS exhibits outstanding bifunctional catalytic activity towards OER and HER. • P and Mo dual doping modulate the electronic structure of CoNiS to enhance the OER and HER activity. • The fabricated PMo-CoNiS delivers a low voltage of 1.48 V at 10 mA cm−2 for overall water splitting. In this work, P and Mo dual-doped CoNiS (PMo-CoNiS) nanosheet arrays were successfully constructed through a common solvothermal treatment. The precise doping of P and Mo species into the CoNiS can regulate the microstructures and meanwhile endow with PMo-CoNiS abundant amorphous/crystalline heterointerfaces, which can adjust the electronic structure, thus enhancing the intrinsic activity of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). As a result, ultra-low overpotentials of merely 156 and 58 mV are required to deliver a current density of 10 mA cm−2 for OER and HER, respectively, and the electrocatalysts PMo-CoNiS also exhibit low Tafel slopes and maintain robust stability for 48 h in alkaline media at a high current density of 50 mA cm−2. In addition, in an assembled electrolyte cell for overall water splitting, a voltage as low as 1.48 V is sufficient to yield a current density of 10 mA cm−2. Density functional theory (DFT) calculations further confirmed that the enhanced OER and HER result from the optimized OH* and H* adsorption energy of PMo-CoNiS due to P, Mo dual doping and generated interfacial effect. This work may offer an avenue for designing low-cost bifunctional catalysts with superior catalytic activity and provide a new application strategy for broader applications in various electrocatalytic fields. [Display omitted] [ABSTRACT FROM AUTHOR]