The hybrid engineering of crystalline NiSex nanorod arrays with amorphous Ni–P film towards promoted overall water electrocatalysis

Abstract

The rational design and facile synthesis of high-efficiency, low-cost, and robust bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are pivotal for hydrogen generation for energy conversion and storage. With this in mind, the synergistic modulation of the architecture, composition, and crystallinity of a non-precious-metal electrocatalyst is considered to be an efficacious strategy to enhance its catalytic activity. Herein, we present a facile route for fabricating a hierarchical Ni–P/NiSe_x hetero-nanostructured material grown in situ on nickel foam (NF) (denoted as Ni–P/NiSe_x/NF), which can act as a bifunctional electrocatalyst, via electrodepositing amorphous Ni–P film on the surface of hydrothermally synthesized crystalline NiSe_x nanorod arrays. The distinctive superhydrophilic 3D structure and useful heterointerface not only afford the greater exposure of active sites, but this material also shows faster charge/mass transport and facilitates the departure of gas bubbles. Meanwhile, benefitting from the regulated electronic structure of NiSe_x and the synergistic effects of outer amorphous Ni–P and inner crystalline NiSe_x, the as-fabricated multi-phase catalyst exhibits simultaneously excellent electrocatalytic performances during the HER (overpotentials of 98 and 165 mV at 10 and 100 mA cm⁻², respectively) and OER (an overpotential of 320 mV at 100 mA cm⁻²) in 1 M KOH electrolyte. Impressively, a Ni–P/NiSe_x/NF sample presents robust stability (100 h) during the OER and HER at a large current density. Significantly, an ultralow cell voltage of 1.536 V is required to deliver a current density of 10 mA cm⁻² in a two-electrode electrolyzer with Ni–P/NiSe_x/NF as both the anode and cathode for overall water splitting (OWS), with the demonstration of remarkable durability, and this material far outperforms many recently reported bifunctional electrocatalysts. This work provides a promising strategy for developing efficient bifunctional catalysts for hydrogen production based on the synergistic engineering of the nanostructure design, composition control, and the use of crystalline states.