Hybridizing amorphous NiOx nanoflakes and Mn-doped Ni2P nanosheet arrays for enhanced overall water electrocatalysis

Abstract

Rational development and facile fabrication of efficient and low-cost bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) play a vital role in hydrogen and oxygen generation by overall water electrocatalysis. Herein, a series of hierarchical core–shell hybrid nanostructured bifunctional electrocatalysts have been successfully synthesized by electrodepositing amorphous nickel oxide nanoflakes (A-NiO_x) on the surface of crystalline Mn-doped Ni₂P nanosheet arrays (Mn₅-Ni₂P). Benefitting from the synergistic effect generated from the outer amorphous NiO_x and inner highly crystalline Mn₅-Ni₂P nanosheets, the optimal A-NiO_x-20/Mn₅-Ni₂P sample exhibits quite low overpotentials for the HER (55 mV) and OER (255 mV) to afford a current density of 10 mA cm⁻² in alkaline electrolyte. Moreover, the two-electrode water electrolysis device only requires a small cell voltage of 1.54 V to deliver 10 mA cm⁻² and shows no obvious attenuation for 20 hours. Our work will provide a valuable method to design and synthesize efficient electrocatalysts for water splitting and other applications of energy conversion and storage.