Motivating high-valence Nb doping by fast molten salt method for NiFe hydroxides toward efficient oxygen evolution reaction

Abstract

High-valence Nb has been proved to be promising to enhance oxygen evolution reaction (OER). However, how to realize the atomic doping of larger-radii Nb is challenging. Herein, an elaborate molten salt method is applied to rapidly incorporate Nb into NiFe-layered double hydroxides (Nb-NiFe-LDH). The fabricated Nb-NiFe-LDH is featured with nano pompons composed of cross-linked hollow nanotubes, which ensures maximum exposure of active sites. Meanwhile, the generated lattice defects can adjust electron density and absorption property of intermediates on the surface, facilitating oxygen evolution. As validation, the obtained Nb-NiFe-LDH exhibits motivated OER activity with overpotential of 242 mV at 50 mA cm−2 and small Tafel slope of 31.3 mV dec−1 as well as long-term stability of 73 h. DFT reveals that such superior OER performance benefits from the fine-tuned surface adsorption ability for reaction intermediates and electron transfer capability as well as optimized oxidation cycle of active metals by synergistic Nb and defects. This work is expected to provide deep insights into the advanced catalysts development via high-valence metal doping achieved by molten salt method.