Development of Novel Hierarchically Microporous-Mesoporous Carbon and Carbon Nanospheres Based Materials and PEMFC Single Cells
Authors: Lust Enn , Sepp Silver , Nerut Jaak , Vaarmets Kersti , Kanarbik Rait , Tallo Indrek , Jäger Rutha , Härk Eneli , Ereth Kasatkin Piia , Taleb Masoud 
Published: February 2020

Development and application of the proton exchange membrane fuel cell (PEMFC) based transport systems is one of the urgent problems for mega-cities and densely populated areas. However, low redox stability of the carbon supports in strongly oxidising/reducing fuel cells working conditions is the major unsolved problem in materials technology, hindering the wide scale application of PEMFC. Therefore the novel hierarchically microporous-mesoporous carbon supports for deposition of various catalytically active particles have been tested in order to establish the best materials with high cyclability. The carbon materials developed and used as PEMFC catalyst supports in this work have been tested for many years in electrical double layer supercapacitors under very high current density pulsation conditions.
In the last years the synthesis methods for carbide derived carbon (C(VC), C(Mo2C), C(TiC), C(SiC) [1, 2] and carbon nanospheres [3, 4] have been developed and corresponding Pt, Ir, Ru-Ir, as well as d-metals nanoclusters activated catalysts have been synthesised [5-8].
All carbon as well as catalyst materials synthesised have hierarchically microporous-mesoporous structure verified by SEM-EDX, FIB-TOF-SIMS, high-resolution TEM and Brunauer-Emmett-Teller gas adsorption methods. The carbon materials have been tested by small angle neutron scattering methods and variable shape of pores has been verified [9].
The Ru, Pt and Ir nanoparticles were deposited onto a carbon support, using the well established liquid-phase reduction methods [5-8]. Thermogravimetric and thermodynamic analysis, X-ray diffraction and Raman spectroscopy methods were used in order to characterize the structure of the materials synthesised. The catalysts prepared were tested as electrodes in the three-electrode as well as in the single cell conditions. The polarization, rotating disk electrode, as well as chronoamperometric measurements were carried out in order to evaluate the activity and stability of the catalyst materials synthesised. The rotating disk electrode data show that the degradation of catalytic activity during 30 cycles was moderate.
The electrochemically active surface area has been calculated from the hydrogen adsorption data. The electrochemical impedance method has been used to calculate the electrolyte resistance, polasization resistance and activation energy values.
The assembled single cells demonstrated excellent cyclability (3000 cycles) and very high catalytic activity, thus noticeably better performance than those based on the traditional Vulcan electrode materials.

Acknowledgements

This work was supported by Estonian Target research project No. IUT20-13, Estonian Centre of Excellence projects (Nos. 3.20101.11-0030 and 2014-2020.4.01.15-0011), and Personal Research Grant PUT55.

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