Bimetallic Fe-Ni phosphide carved nanoframes toward efficient overall water splitting and potassium-ion storage

Abstract

Developing high-performance and cost-effective electrode materials to advance the overall water splitting and electrochemical potassium-ion storage has thus far remains appealing yet challenging. Herein, bimetallic Fe-Ni phosphide (FNP) nanoframes harvesting three-dimensional carved frameworks have been fabricated in a scalable and controllable fashion. Thus-derived FNP nanoframes have been demonstrated as efficient bifunctional electrocatalysts for overall water splitting, comparing favorably with the benchmark performance of the IrO2/Pt couple. Such excellent water splitting features can be attributed to the enhanced charge transfer, enlarged active surface area, facilitated electrolyte transport and promoted gas release. Density functional theory calculations reveal that the FNP owns the lowest free energy barrier of the rate-determined step for hydrogen evolution in the alkaline media as compared to the mono-metallic Fe2P and Ni2P species. In addition, as an anode candidate, FNP possesses outstanding potassium ion storage performances, showing high specific capacity (168 mAh g−1 at 50 mA g−1) and long cycle life (83% capacity retention after 700 cycles at 200 mA g−1). As a proof-of-concept demonstration, all-FNP, KIB-based self-powering water-splitting system can further be constructed, opening up exciting opportunities for the real applications of renewable energy on a basis of as-designed multifunctional FNP architectures.