Hierarchical iron nickel oxide architectures derived from metal-organic frameworks as efficient electrocatalysts for oxygen evolution reaction

In this study, a series of iron nickel oxide (Fe-Ni-O-x) architectures with different Fe/Ni ratios are synthesized by using corresponding Fe-Ni-based metal-organic frameworks (MOFs) as self-templates for the first time. The characterization on microstructures suggest that Fe/Ni ratio significantly affects the morphology and phase composition of Fe-Ni-O-x architectures. The Fe-rich samples exhibit spindle-like structures while the Ni-rich samples consist of irregular nanoparticle aggregates, and the higher Ni ratio is favorable for the formation of Fe-Ni-spinel strucutre in product. Serving as nonprecious electrocatalysts, the Fe-Ni-O-x architectures exhibit the remarkable electrocatalytic activity toward oxygen evolution reaction (OER) in alkaline medium, which is found to be closely dependent on composition of Fe-Ni-O-x catalysts. The active phase of spinel-structured NiFe2O4 plays a dominating role in enhancing the electrocatalytic OER activity of the Fe-Ni-O-x architectures. Based on the X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy analysis, the possible OER mechanism of the Fe-Ni-O-x architectures is unraveled as well. (C) 2016 Elsevier Ltd. All rights reserved.