Self-Anti-Stacking 2D Metal Phosphide Loop-Sheet Heterostructures by Edge-Topological Regulation for Highly Efficient Water Oxidation

2D metal phosphide loop-sheet heterostructures are controllably synthesized by edge-topological regulation, where Ni₂P nanosheets are edge-confined by the N-doped carbon loop, containing ultrafine NiFeP nanocrystals (denoted as NiFeP@NC/Ni₂P). This loop-sheet feature with lifted-edges prevents the stacking of nanosheets and induces accessible open channels for catalytic site exposure and gas bubble release. Importantly, these NiFeP@NC/Ni₂P hybrids exhibit a remarkable oxygen evolution activity with an overpotential of 223 mV at 20 mA cm⁻² and a Tafel slope of 46.1 mV dec⁻¹, constituting the record-high performance among reported metal phosphide electrocatalysts. The NiFeP@NC/Ni₂P hybrids are also employed as both anode and cathode to achieve an alkaline electrolyzer for overall water splitting, delivering a current density of 10 mA cm⁻² with a voltage of 1.57 V, comparable to that of the commercial Pt/C||RuO₂ couple (1.56 V). Moreover, a photovoltaic–electrolysis coupling system can as well be effectively established for robust overall water splitting. Evidently, this ingenious protocol would expand the toolbox for designing efficient 2D nanomaterials for practical applications.