Interfacial Regulation of Rice-Grain-like Iron–Nickel Phosphide Nanorods on Phosphorus-Doped Graphene Architectures as Bifunctional Electrocatalysts for Water Splitting

The design of bimetallic metal-organic frameworks (MOFs) with a hierarchical structure is important to improve the electrocatalytic performance of catalysts due to their synergistic effect on different metal ions. In this work, the catalyst comprises bimetallic iron-nickel MOF-derived FeNi phosphides, intricately integrated with phosphorus-doped reduced graphene oxide architectures (FeNi₂P-C/P-rGA) through the hydrothermal and phosphating treatments. The hierarchical architecture of the catalyst is beneficial for exposing active sites and facilitating electron transfer. The FeNi₂P-C/P-rGA catalyst exhibits excellent performance in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline electrolytes. Notably, FeNi₂P-C/P-rGA requires only the overpotential of 93 and 210 mV to achieve a current density of 10 mA cm^-2 for the HER and OER with small values of Tafel slope and charge transfer resistance, respectively. Furthermore, the catalyst exhibits boosted activity for overall water splitting with a low potential of 1.56 V. This work can be considered to extend the design of multilevel catalysts in the application of water splitting.