Three-dimensional ordered macroporous design of heterogeneous nickel-iron phosphide as bifunctional electrocatalyst for enhanced overall water splitting

Abstract

Developing high-performance oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) bifunctional electrocatalysts is essential for overall water splitting. Herein, heterogeneous engineering-induced strategy was demonstrated by the synthesis of bimetallic Ni2P/FeP/Fe2P heterostructure with three-dimensional ordered macroporous structure (3DOM-Ni2P/FexP) as bifunctional catalyst. The heterogeneous interfaces formed by the three distinct phases can adjust the electron distribution and create abundant active sites to improve the catalytic performance. The 3DOM structure provides large specific surface area and good mass transfer for electrocatalytic reaction occurring at the solid-gas-electrolyte multiphase interfaces. Accordingly, the 3DOM-Ni2P/FexP showed remarkable OER and HER electrocatalytic activity in 1 M KOH electrolyte. Moreover, it demonstrates that the 3DOM-Ni2P/FexP turns out oxidation and transformation during the OER process. Computational results reveal the synergy of the converted Fe2O3/NiOOH, promoting the OER reaction energetics. In addition, an alkaline electrolyzer with the 3DOM-Ni2P/FexP as both the cathode and anode achieves excellent overall water splitting performance, with only 1.54 V voltage to obtain the current density of 10 mA cm−2. This present study gives a novel concept of heterogeneous engineering-induced bimetallic phosphide with macroporous structure design towards the high-performing OER and HER bifunctional electrocatalysts evolvement.