Anion exchange membrane fuel cells (AEMFCs) have been regarded as a promising low-cost alternative to proton exchange membrane fuel cells (PEMFCs) due to their potential to utilize platinum group metal (PGM) free catalysts and their recently demonstrated improvement in power density. However, the development of highly active and stable PGM-free electrocatalysts for the hydrogen oxidation reaction (HOR) in alkaline solutions remains a significant challenge. In this study, reactive spray deposition technology (RSDT) is used to fabricate a set of Ni/CeO2/C catalysts, and their activity toward the HOR is investigated as a function of the nanoparticle size. The structural and morphological characterization of as synthesized Ni/CeO2/C catalysts confirms that the RSDT is capable of
The alkaline operating environment of anion-exchange membrane (AEM) fuel cells (AEMFCs) makes it possible to employ a wide variety of catalysts, including platinum group metals (PGMs) as well as PGM-free materials. However, little is understood about radical formation during AEMFC operation with different catalysts and their implications. In this investigation, we utilized spin-trapping and electron-paramagnetic resonance measurements to measure and identify the radicals produced on selected PGM and PGM-free oxygen-reduction reaction catalysts. To the best of our knowledge, this is an original study exploring radical formation on different classes of catalysts in operando AEMFCs. This work highlights an unexplored radical
We present a model-based analysis of the transport of anions in anion exchange membranes (AEMs) with the aim of understanding the decarbonation process and its dynamics. The dynamic simulation model covers the diffusive and migrative transport of water, carbonate anions, and hydroxide anions through an AEM. To the best of our knowledge, this is the first model studying decarbonation process in AEMs. The model is validated using decarbonation data from anion conductivity measurements of ten different AEM materials. Driven by migrative transport, strong concentration gradients develop inside the membranes. A parameter study reveals that the ion-exchange capacity and the applied
Nickel-based catalysts reach a high activity for the hydrogen oxidation reaction (HOR) in anion exchange membrane fuel cells. While incorporation of iron significantly decreases the HOR overpotential on NiFe-based catalysts, the reason for the enhanced activity remains only partially understood. For the first time, in situ 57Fe Mössbauer spectroscopy is used to gain insights into the iron-related composition at different potentials. The aim is to evaluate which changes occur on iron at potentials relevant for the HOR on the active Ni sites. It is found that different pre-conditionings at low potentials stabilize the iron at a low oxidation state as
Platinum group metal (PGM)-free oxygen reduction reaction (ORR) catalysts are of utmost importance for the rapid development of anion-exchange membrane fuel cell (AEMFC) technology. In this work, we demonstrate the improved ORR performance and stability of Co and Fe oxide-decorated/N-doped reduced graphene oxide (CoOx-Fe3O4/N-rGO) prepared via a hydrothermal method at the low temperature of 150 °C. The catalysts were characterized thoroughly using transmission electron microscopy, high-angle annular dark field-scanning electron microscopy, X-ray diffraction, N2 physisorption, Raman spectroscopy, and X-ray photoelectron spectroscopy to obtain information about morphology, elemental distribution, phases, porosity, defects, and surface elemental compositions. Significant ORR activity improvement (130 mV@-1.5 mA cm−2)
Ammonia has recently been proposed as a promising candidate fuel for anion-exchange membrane fuel cell (AEMFC) technology. Direct ammonia AEMFCs (DA-AEMFCs) are a carbon-free technology that combines the ammonia's high energy density with the fuel cells' high efficiency. However, two major challenges face this technology: ammonia crossover (due to ammonia's high solubility in water) and sluggish ammonia oxidation reaction (AOR). We have developed, applied, and presented a one-dimensional and transient model of a DA-AEMFC system to address these challenges. Excellent agreement is obtained between the experimentally-measured and computationally-simulated performance of DA-AEMFCs operating at 100 and 120 °C with KOH-free anode feed.
Recently, the development of durable anion-exchange membrane fuel cells (AEMFCs) has increased in intensity due to their potential to use low-cost, sustainable components. However, the decomposition of the quaternary ammonium (QA) cationic groups in the anion-exchange membranes (AEMs) during cell operation is still a major challenge. Many different QA types and functionalized polymers have been proposed that achieve high AEM stabilities in strongly alkaline aqueous solutions. We previously developed an ex situ technique to measure AEM alkaline stabilities in an environment that simulates the low-hydration conditions in an operating AEMFC. However, this method required the AEMs to be soluble in DMSO solvent,
In recent years, the development of anion-exchange membranes (AEMs) for anion-exchange membrane fuel cell (AEMFC) applications has been rapidly growing due to their numerous advantages over mainstream proton-exchange membrane fuel cells. However, a major challenge in the development of practical AEMs is the low chemical stability of the AEM quaternary ammonium (QA) functional groups in the strongly alkaline and the relatively dry environment produced during operation of the AEMFC. Herein, we investigate the effect of polymer chain folding on the chemical stability of the QA groups. While these polymers have virtually the same chemical composition, their molecular architectures are quite
In this work, doped nanocarbon electrocatalysts for electrochemical oxygen reduction reaction (ORR) are prepared by high-temperature pyrolysis from Honeyol, cobalt and iron salts, and dicyandiamide. MgO-based inorganic templates are further used to increase the mesoporosity of the prepared catalyst materials. The templated bimetallic electrocatalyst containing iron and cobalt (FeCoNC-MgOAc) showed excellent stability and remarkable ORR performance in rotating disk electrode testing in alkaline conditions. The catalyst was further tested in anion-exchange membrane fuel cells (AEMFCs), where FeCoNC-MgOAc performed significantly better than the nontemplated material (FeCoNC), yielding a peak power density (Pmax) of 0.92 W cm–2 surpassing that of the commercial Pt/C
Authors: Sapir Willdorf-Cohen, Alexander Kaushansky, Dario R. Dekel, and Charles E. Diesendruck
Solvent molecules are known to affect chemical reactions, especially if they interact with one or more of the reactants or catalysts. In ion microsolvation, i.e., solvent molecules in the first solvation sphere, strong electronic interactions are created, leading to significant changes in charge distribution and consequently on their nucleophilicity/electrophilicity and acidity/basicity. Despite a long history of research in the field, fundamental issues regarding the effects of ion microsolvation are still open, especially in the condensed phase. Using reactions between hydroxide and relatively stable quaternary ammonium salts as an example, we show that water microsolvation
