Sn-doping facilitating electronic modulation and surface reconstruction of 3D hierarchical nanoflowers assembled by Fe(PO3)2/Ni2P nanosheets to trigger oxidation evolution reaction

Abstract

Transition metal phosphides (TMPs) are considered as potential alternative for noble-metal oxides in oxygen evolution reaction (OER), but the limited intrinsic activity hinders its practical application. Herein, high-valence Sn doped 3D hierarchical nanoflowers assembled by Fe(PO3)2/Ni2P nanosheets (Sn-Fe(PO3)2/Ni2P) were fabricated by hydrothermal and thermal phosphating process. The XPS characterization and in-situ UV–vis spectroscopy unveil that Sn doping can modulate the electronic structure of Ni2P, stabilize Fe2+, and further facilitate the surface reconstruction of Sn-Fe(PO3)2/Ni2P to generate Ni/FeOOH as active phases. And as a result, the optimal Sn-Fe(PO3)2/Ni2P displays a low overpotential of 229 mV at 10 mA cm−2 with small Tafel slope (43 mV dec−1) and high stability at 100 mA cm−2. Beyond, the overall alkaline water splitting with Sn-Fe(PO3)2/Ni2P/NF and Pt/C/NF as anode and cathode exhibits small cell voltage of 1.63 V at 100 mA cm−2, and excellent stability for 80 h at 100 mA cm−2. The superior performance of Sn-Fe(PO3)2/Ni2P is ascribed to the rich mesopore for exposure more active sites, rapid deprotonation of OH- and the increased charge transfer after high-valance Sn4+ doping. This work provides a new avenue of accelerating surface reconstruction and optimizing electronic structure by high-valence metal doping for design high-efficiency electrocatalysts.