Self-supported ternary Ni-Fe-P nanosheets derived from metal-organic frameworks as efficient overall water splitting electrocatalysts

Developing cost-effective, highly-efficient and stable electrocatalysts is of significance to replace noble metal based materials for overall water electrolysis. In this paper, nickel-iron phosphide nanosheets on nickel foam (Ni-Fe-P/NF) were synthesized through in-situ chemical etching and subsequently phosphating treatment. The Ni foam utilized in this work not only serves as conductive substrate and metal current collector, but also as nickel source for the growth of metal organic frameworks (i.e. Prussian blue analogue pyramids), which were then converted to Ni-Fe-P nanosheets via phosphating. Benefiting from the unique nanostructure, Fe incorporation, and the high conductivity of nickel foam, the resulting Ni-Fe-P/NF could be used as self-supported and binder-free working electrode with superior overall electrochemical water splitting performance. Electrochemical measurement demonstrates that the Ni-Fe-P/NF exhibits excellent electrocatalytic activities with overpotentials of 98 mV for HER and 168 mV for OER to deliver current densities of 10 mA cm(-2) in 1 M KOH solution. Furthermore, the Ni-Fe-P/NF catalyst was also employed as both as anode and cathode for overall water electrolysis, and shows extraordinary activities with low voltage of only 1.486 V to yield 10 mA cm(-2) and outstanding cycling stability with negligible voltage elevation after chronopotentiometry determination for 200 h. This work highlights that direct growth of metal organic frameworks on conductive substrates is an effective method to explore electrocatalysts for multifunctional electrochemical applications. (c) 2017 Elsevier Ltd. All rights reserved.