Electron Manipulation and Surface Reconstruction of Bimetallic Iron–Nickel Phosphide Nanotubes for Enhanced Alkaline Water Electrolysis

Abstract

Developing high‐efficiency and stable bifunctional electrocatalysts for water splitting remains a great challenge. Herein, NiMoO4 nanowires as sacrificial templates to synthesize Mo‐doped NiFe Prussian blue analogs are employed, which can be easily phosphorized to Mo‐doped Fe2xNi2(1‐x)P nanotubes (Mo‐FeNiP NTs). This synthesis method enables the controlled etching of NiMoO4 nanowires that results in a unique hollow nanotube architecture. As a bifunctional catalyst, the Mo‐FeNiP NTs present lower overpotential and Tafel slope of 151.3 (232.6) mV at 100 mA cm−2 and 76.2 (64.7) mV dec−1 for HER (OER), respectively. Additionally, it only requires an ultralow cell voltage of 1.47 V to achieve 10 mA cm−2 for overall water splitting and can steadily operate for 200 h at 100 mA cm−2. First‐principles calculations demonstrate that Mo doping can effectively adjust the electron redistribution of the Ni hollow sites to optimize the hydrogen adsorption‐free energy for HER. Besides, in situ Raman characterization reveals the dissolving of doped Mo can promote a rapid surface reconstruction on Mo‐FeNiP NTs to dynamically stable (Fe)Ni‐oxyhydroxide layers, serving as the actual active species for OER. The work proposes a rational approach addressed by electron manipulation and surface reconstruction of bimetallic phosphides to regulate both the HER and OER activity.