Self-supported ternary (NixFey)2P nanoplates arrays as an efficient bifunctional electrocatalyst for overall water splitting

Highlights: • Ternary (Ni_xFe_y)₂P nanoplates arrays on nickel foams were prepared. • Combination of electrodeposition and phosphorization technologies. • Bifunctional electrocatalyst for overall water splitting. • Bimetallic synergistic effect in transition metal phosphides. -- Abstract: Developing non-precious metal bifunctional electrocatalysts for effective overall water splitting is promising to realize high-efficient renewable energy production. In this work, ternary (Ni_xFe_y)₂P nanoplates arrays on 3D self-supported nickel foams were prepared through a simple coelectrodeposition followed by phosphorization. The synthesized (Ni_xFe_y)₂P nanoplates arrays showed remarkable bifunctional electrocatalytic performances in the KOH electrolyte, with the Tafel slopes of 57.8 mV·dec⁻¹ and 53.6 mV·dec⁻¹, and low overpotentials of 115 mV and 182 mV to reach a current density of 10 mA cm⁻² for hydrogen evolution reaction and oxygen evolution reaction, respectively. In addition, the optimized (Ni_0.66Fe_0.33)₂P anode and cathode demonstrated outstanding ability for overall water splitting in the two-electrode alkaline electrolyzer, generating a current density of 10 mA cm⁻² at the applied cell voltage of 1.61 V. This benefited by the active surface to expedite reactants absorption, faster electron transport in the solid-liquid interface and reduced charge-transfer resistance due to the bimetallic synergistic effect. This delicate design of bifunctional transition metal phosphides provides a potential approach to realize water reuse and energy regeneration by the full water splitting.