Oxygen-Doped Nickel Iron Phosphide Nanocube Arrays Grown on Ni Foam for Oxygen Evolution Electrocatalysis

Abstract

A rationally designed oxygen evolution reaction (OER) catalyst with advanced structural and compositional superiority is highly desirable to optimize electrocatalytic performance. Prussian blue analogues (PBAs) with adjustable element compositions and accessible porous structures represent a promising precursor for the preparation of OER catalysts. Herein, oxygen-doped nickel iron phosphide nanocube arrays (Ni₂ P/(NiFe)₂ P(O) NAs) grown on Ni foam is rationally designed and fabricated from PBAs. The porous structure and the synergistic effect of Ni and Fe enable superior electrocatalytic performance and stability toward the OER in alkaline electrolytes. Density functional theory calculations reveal that Fe-incorporated Ni₂ P can generate new active sites on the Fe atoms, and the energy barriers of the intermediates and products are decreased efficiently in the presence of surface doped oxygen, both processes are crucial factors for enhanced catalytic performances. In 1 m KOH, the Ni₂ P/(NiFe)₂ P(O) NAs afford current densities of 10 and 800 mA cm^-2 at overpotentials of 150 and 530 mV, respectively, which outperform the commercial noble metal IrO₂ . Ni₂ P/(NiFe)₂ P(O) NAs also have long-term stability over 100 h at a high current density. The present approach may provide a new avenue for the controlled assembly of nanoarrays for energy storage and conversion applications.

Keywords: Prussian-blue-analogue; metal phosphide; nanoarrays; nanocube; oxygen evolution reaction.