FORMATION OF ACTIVE INTERPHASE ON THE IRON PARTICLES IN C/PVDF MEDIA
Panteleymonov R.A.1, Sherbatuk I.M.2, Boychuk O.V.1, Pershina K.D.1,2
1VI.Vernadskii Institute of General and Inorganic Chemistry,
Palladin Ave, 32/34, 03142, Kyiv, Ukraine, e-mail:katherinepersh@gmail.com
2Joint Department of Electrochemical Energy Systems
Vernadsky Ave, 38, 03142, Kyiv, Ukraine
The use of catalyst support materials is essential for nanostructured catalytic systems for many energy-transformed devices. Ideal catalyst carrier should possess such properties:  high conductivity, high surface area, low cost, electrochemical inertness, and stability.  Carbon-based materials have been used as catalyst supports for a long time due to their unique properties such as, physical stability, excellent conductivity, and high surface area. That is why, the study of the formation of new interphases on the iron surface in the composite Fe/C/PVDF films and their impact on thermoelectric properties of composites are actual for the development of a new generation of energy storage.  The aim of this work was, the study differences in the quantity of the elements and their ratio on the surface of iron particles and in the volume of the carbon phase. The micromorphological studies of composite samples and quantitative microanalysis of the surface were performed on a scanning electron microscope Tescan Mira 3 LMU, and on energy dispersed spectrometer Oxford Instruments X-Max 80 mm2 SDD (table).
Table. The composition of the surface of the composite film, wt.%
Zones film	C	O	Fe	F	Ratio (formula)		
Zone 1	23.21±2.1	48.83±0.3	26.23±0.5	0.77±0.5	FeC4O6		
Zone 2 	96.44±2.1	2.79±0.3	26.23±0.5	0.77±0.5	Fe3O C48		
The difference in the oxygen content on the surface of iron particles and in the volume of graphite indicates the higher impact of the PVDF in the case of iron particles. It may be connected with the ability of Fe coated by Fe3O4 in the presence of graphite to induce the reduction of Fe3+ to Fe2+ with the generation of free high reactive oxygen [1]. High reactive oxygen is able to form -O–O- and C=O groups on PVDF mainly due to exchanging F in C-F [2]. So, on the surface of iron particles forms a new interface (with size 30 ÷ 80 nm) saturated by active oxygen compounds with high mobility. Confirmation of high mobility of oxygen species is the analysis of graphite in the volume, where at a distance of more than 30 μm the presence of oxygen was found, but in smaller quantities. Also, in this region was detected Fe. If the presence of Fe2O3 takes place, the probability of the formation Fe3C increases in the graphite space. Thus, the simultaneous presence of proactive compounds of oxygen and iron carbide should significantly affect the formation of gradient phenomena and change the thermoelectric properties of the whole system.
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