Stacking Faults Triggered Strain Engineering of ZIF-67 derived Ni-Co Bimetal Phosphide for Enhanced Overall Water Splitting

Abstract 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.