Activation of bimetallic PtFe nanoparticles with zeolite-type cesium salts of vanadium-substituted polyoxometallates toward electroreduction of oxygen at low Pt loadings for fuel cells

Abstract

The catalytic activity of commercial carbon-supported PtFe (PtFe/C) nanoparticles admixed with mesoporous polyoxometalate Cs3H3PMo9V3O40, (POM3-3–9), has been evaluated towards oxygen reduction reaction (ORR) in acid medium. The polyoxometalate cesium salt co-catalyst/co-support has been prepared by titration using the aqueous solution of phosphovanadomolibdic acid. The synthesized material has been characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results confirm formation of the polyoxometalate salt with the characteristic Keggin-type structure. The composite catalyst has been prepared by mixing the POM3-3–9 sample with the commercial PtFe/C by sonication. The diagnostic rotating ring-disk voltammetric studies are consistent with good performance of the system with low Pt loading during ORR. The fuel cell membrane electrode assembly (MEA) utilizing the PtFe/POM-based cathode has exhibited comparable or better performance (at relative humidity on the level of 100, 62, and 17%), in comparison to the commercial MEA with higher Pt loading at the cathode. Furthermore, based on the cell potential and power density polarization curves, noticeable improvements in the fuel cell behavior have been observed at the low relative humidity (17%). Finally, the accelerated stress test, which uses the potential square wave between 0.4 V and 0.8 V, has been performed to evaluate MEA stability for at least 100 h. It has been demonstrated that, after initial losses, the proposed catalytic system seems to retain stable performance and good morphological rigidity.

An Iron-Doped Calcium Titanate Cocatalyst for the Oxygen Reduction Reaction

“…Finally, both carbon corrosion and platinum nanoparticles dissolution processes, responsible for the catalytic activity loss when the fuel cell was working, might be mitigated when adding a metal oxide [49]. Therefore, the electrocatalytic properties of composite electrodes are expected to improve, increasing the amount of the inorganic additive.…”

“…However, the Pt/C:CTFO 1:0.5 catalyst showed a lower ECSA value compared to the other composite ink, revealing that a poor amount of additive could not be sufficient to optimize the Pt accessibility and utilization and consequently improve the Pt/C catalytic activity. Finally, both carbon corrosion and platinum nanoparticles dissolution processes, responsible for the catalytic activity loss when the fuel cell was working, might be mitigated when adding a metal oxide [49]. Therefore, the electrocatalytic properties of composite electrodes are expected to improve, increasing the amount of the inorganic additive.…”