![]() Several recent papers have considered the potential use of these materials in fuel cells due to their ability to strongly adsorb metal catalyst inside the micro-meso pores and their high acidity, which can be exploited to improve both durability and performance. Heteropolyacids (HPAs) and polyoxometalates (POMs) are inorganic compounds used since before 1900, which are unmatched not only in terms of molecular and electronic structural versatility but also in terms of reactivity and relevance to analytical chemistry, catalysis, biology, medicine, geochemistry, materials science, and topology. Among possible strategies of the cost-reducing and improving durability is designing a carbon co-support that could allow improving metal active phase dispersion and limiting aggregation upon working conditions. The decrease of Pt loading under 0.2 mg cm −2 maintaining the membrane electrode assembly (MEA) performance of 1000 mW cm −2, together with low relative humidity (RH) operation and the enhancement of MEA lifetime are some of the important targets aimed at by the US Department of Energy (DOE) for 2020. Therefore, in recent years, most of the research efforts have been devoted to reducing the cathode Pt loadings, without loss of performance and durability. In fact, automotive and stationary fuel cell applications are typically limited to about 1700 h and 10,000 h of operations, respectively, while at least 5000 h and 40,000 h of continuous operation are required. This phenomenon leads to the dissolution of Pt particles, followed by their re-deposition that increases the particle’s size and reduces active electrochemical surface area. Another obstacle to the full commercialization of the PEMFCs constitutes their short lifetime, which is commonly caused by catalyst degradation at the cathode side through the development of positive potentials inducing carbon support corrosion. Moreover, it has to be emphasized that the Pt loading is usually about 5–10 times higher on the cathode than on the anode due to the much slower kinetics of ORR than the HOR. However, the widespread commercialization of PEMFC technology has been greatly hindered mainly due to the high cost and scarcity of Pt materials. At the current stage of the technology, the most effective catalysts for the hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR) are platinum-based materials. The basic structure of a PEMFC consists of a perfluorosulfonate proton exchange membrane in contact with porous electrodes, anode and cathode, coated with a catalyst to let the electrochemical reactions occur on both sides. Among various types of FCs, the low-temperature proton exchange membrane fuel cells (PEMFC) are the most promising candidates for clean and efficient energy conversion in portable and stationary small devices, as well as electric vehicle applications. Therefore, many investigations have focused on the development of fuel cells (FCs), which have several benefits such as high efficiency, silent operating modes, low pollution level, and high durability. Nowadays, under current circumstances, where the energy needs grow daily and the extensive use of fossil fuels leads to severe environmental issues, the matter of alternative energy sources raises rapidly. It has been demonstrated that, after initial losses, the proposed catalytic system seems to retain stable performance and good morphological rigidity. 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. 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%). 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. The diagnostic rotating ring-disk voltammetric studies are consistent with good performance of the system with low Pt loading during ORR. ![]() The composite catalyst has been prepared by mixing the POM3-3–9 sample with the commercial PtFe/C by sonication. The results confirm formation of the polyoxometalate salt with the characteristic Keggin-type structure. The synthesized material has been characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The polyoxometalate cesium salt co-catalyst/co-support has been prepared by titration using the aqueous solution of phosphovanadomolibdic acid. The catalytic activity of commercial carbon-supported PtFe (PtFe/C) nanoparticles admixed with mesoporous polyoxometalate Cs 3H 3PMo 9V 3O 40, (POM3-3–9), has been evaluated towards oxygen reduction reaction (ORR) in acid medium.
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