Prussian blue analogue-derived Mn-Fe oxide nanocubes with controllable crystal structure and crystallinity as highly efficient OER electrocatalysts

A series of ternary manganese iron oxides with different crystal structures, oxidation states and crystallinities were successfully fabricated by modulating the calcination conditions of Mn-Fe Prussian blue analogue (PBA) precursor (Mn-3 [Fe(CN)(6)](2)center dot nH(2)O). The obtained Mn-Fe oxides retained the nanocubic morphology of the PBA precursor, and a mesoporous structure was acquired as a result of gas molecule release during the pyrolysis process. Electrochemical oxygen evolution reaction (OER) activity of the asprepared catalysts was tested, and among the bimetallic oxides, the catalyst that had a crystal structure similar to cubic bixbyite Ma(1.2)Fe(0.8)O(3) (space group: la-3) with low crystallinity exhibited the most advanced OER activity. An overpotential of only 245 mV was required to achieve a current density of 10 mA cm(-2), and the Tafel slope value was only 38 mV dec(-1). The excellent OER activity is likely due to the hollow porous morphology of the samples, the synergistic effect of Mn and Fe, the defect-rich low crystallinity of the catalyst, and the cubic Mn1.2Fe0.8O3 structure (space group: la-3), which has an intrinsic activity superior to that of spinet Ma(1)(.)(8)Fe(1)(.)(2)O(4). (C) 2019 Elsevier B.V. All rights reserved.