Stacking faults triggered strain engineering of ZIF-67 derived Ni-Co bimetal phosphide for enhanced overall water splitting

Structure modulation of transition metal phosphides at the atomic scale can significantly modify their catalytic properties. Herein, stacking faults abundant Ni₂P/Co₂P electrocatalysts with outstanding bifunctional oxygen evolution and hydrogen evolution property have been prepared. The stacking faults are formed by slow dissolution of Ni substrate by Mo⁶⁺ and further redeposition of Ni²⁺ during the growth of Co(OH)F crystals. Unprecedentedly, the distinct mechanistic etching-redeposition pathway dictated by the stacking faults, heterostructures and crystal lattice deformation leads to lattice expansion of Co₂P and enables preferred reactants adsorption. Electrolysis cell employing Ni₂P/Co₂P electrocatalysts as a bifunctional catalyst for both the cathode and the anode delivers a current density of 10 mA cm⁻² at a cell voltage of 1.57 V, which is comparable to the integrated Pt/C and IrO₂ counterparts. The exceptional electrocatalytic performance of Co₂P/Ni₂P-x%Mo indicates the redeposition mechanism a new methodology to modulate the structure and surface reactivity of electrocatalysts.