Phosphorus Vacancies Induced Electron Redistribution of Ni-CoP_1-x/Ti₃C₂ Boosting Bimetallic Redox Activity for...

Defect engineering is recognized as an effective strategy to address the sluggish reaction kinetics of cobalt phosphide (CoP). Herein, nickel-doped CoP nanosheet arrays with different phosphorus vacancies (Ni-CoP_1-x) are vertically grown on both sides of alkali-induced 3D crumpled Ti₃C₂ nanosheets. P vacancies can regulate the electronic structure of Ni-CoP_1-x/Ti₃C₂, inducing additional active sites and facilitating electron transfer, thereby enhancing the reaction kinetics. Meanwhile, 3D Ti₃C₂ serves as a highly conductive and elastic substrate, boosting charge transport and mitigating volume changes of Ni-CoP_1-x during charge and discharge cycles. The unique 3D hierarchical structure promotes the exposure of more active sites and shortens the ion transport path. As a result, the optimal Ni-CoP_1-x/Ti₃C₂-3 electrode shows a high specific capacity of 1058 C g^-1 at 1 A g^-1 and an improved rate capability, which are attributed to the enhanced adsorption of OH^- ions and the upward shift in d-band centers of Ni 3d and Co 3d, as confirmed by density functional theory (DFT) calculations. The assembled Ni-CoP_1-x/Ti₃C₂-3//AC hybrid supercapacitor (HSC) exhibits a high energy density of 46.0 Wh kg^-1 at 572.2 W kg^-1. This work presents an effective strategy for designing transition metal compounds for high-performance energy storage.