N-doped graphene layers encapsulated NiFe alloy nanoparticles derived from MOFs with superior electrochemical performance for oxygen evolution reaction.

Yi Feng,Ungyu Paik,Xin-Yao Yu

doi:10.1038/srep34004

Abstract

Water splitting, an efficient approach for hydrogen production, is often hindered by unfavorable kinetics of oxygen evolution reaction (OER). In order to reduce the overpotential, noble metal oxides-based electrocatalysts like RuO2 and IrO2 are usually utilized. However, due to their scarcity, the development of cost-effective non-precious OER electrocatalysts with high efficiency and good stability is urgently required. Herein, we report a facile one-step annealing of metal-organic frameworks (MOFs) strategy to synthesize N-doped graphene layers encapsulated NiFe alloy nanoparticles (NiFe@C). Through tuning the nanoparticle size and calcination temperature, NiFe@C with an average size of around 16 nm obtained at 700 °C exhibits superior OER performance with an overpotential of only 281 mV at 10 mA cm−2 and high durability. The facile synthesis method and excellent electrochemical performance show great potential of NiFe@C in replacing the precious metal-based electrocatalysts in the OER.

Highlights

Prussian blue analogue (PBA), as a subclass of crystalline metal-organic frameworks (MOFs) with diverse compositions and morphologies has been extensively investigated as precursors to synthesize various functional materials[12,13,14,15]
The gel-like character is confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) measurements (Supplementary Fig. 2a,b)
When 180 mg of trisodium citrate dehydrate (TSC) are used, NiFe-PBA nanocubes with size of 40 nm is obtained, as confirmed by SEM and X-ray diffraction (XRD) (Supplementary Figs 1 and 3a)

Summary

Introduction

Prussian blue analogue (PBA), as a subclass of crystalline metal-organic frameworks (MOFs) with diverse compositions and morphologies has been extensively investigated as precursors to synthesize various functional materials[12,13,14,15]. As PBAs are rich in N-containing organic ligands (CN- groups) and transition metal cations, they are believed to be promising precursors to prepare highly nitrogen doped carbon with metal or metal alloy nanoparticles. Ni and Fe cations from the precursor will be reduced to form NiFe alloy nanoparticles, while CN- group linkers will form N-doped graphene layers outside the alloy nanoparticles during annealing process under high temperature and Ar atmosphere. The NiFe@C electrocatalyst with size of about 16 nm synthesized at 700 °C exhibit excellent catalytic activity and stability for OER

Methods

Results

Conclusion