Explore the vast range of titles available.

A nickel ferrite was prepared by a liquid‐phase method and used as an oxygen evolution catalyst in an anion exchange membrane electrolyser. A complete physicochemical characterization of the catalyst was performed through X‐ray diffraction (XRD), Transmission electron microscopy (TEM) and X‐ray photoelectron spectroscopy (XPS). Then, the nickel ferrite was deposited by spray coating technique onto a Fumasep® FAA3‐50 anion‐exchange membrane to realize a catalyst‐coated membrane (CCM), and tested in a 5 cm2 single cell setup in the so‐called zero‐gap configuration. At 60 °C and 2.2 V, a current density of 3 A/cm2 was reached, which is higher than that obtained with NiO and IrO2 commercial catalysts. Moreover, a chronoamperometric test of 120 h highlighted the good stability of the synthesized catalyst. Nickel ferrite for Anion Exchange Membrane Electrolyser: Home‐made nickel ferrite, characterised by low cristallyte size (3.3 nm), was employed as an oxygen evolution catalyst in anion exchange membrane water electrolyser achieving the highest current density values (at 2 V) among the non‐PGM‐anode‐based MEAs.

Polymer Electrolyte Fuel Cells (PEFCs) are one of the most promising power generation systems. The main component of a PEFC is the proton exchange membrane (PEM), object of intense research to improve the efficiency of the cell. The most commonly and commercially successful used PEMs are Nafion™ perfluorosulfonic acid (PFSA) membranes, taken as a reference for the development of innovative and alternative membranes. Usually, these membranes undergo different pre-treatments to enhance their characteristics. With the aim of understanding the utility and the effects of such pre-treatments, in this study, a commercial Nafion™ NR212 membrane was subjected to two different chemical pre-treatments, before usage. HNO3 or H2O2 were selected as chemical agents because the most widely used ones in the procedure protocols in order to prepare the membrane in a well-defined reference state. The pre-treated membranes properties were compared to an untreated membrane, used as-received. The investigation has showed that the pre-treatments enhance the hydrophilicity and increase the water molecules coordinated to the sulphonic groups in the membrane structure, on the other hand the swelling of the membranes also increases. As a consequence, the untreated membrane shows a better mechanical resistance, a good electrochemical performance and durability in fuel cell operations, orienting toward the use of the NR212 membrane without any chemical pre-treatment.

High‐performance platinum group metal‐free (PGM‐free) electrocatalysts were prepared from porous organic polymers (POPs) precursors with highly‐porous structures and adjustable surface area. A resin phenol‐melamine‐based POP and an iron salt were used to synthesize Fe−N−C catalysts with different iron contents (0.2–1.3 wt.%). Electrochemical and spectroscopical characterization allowed us to elucidate the effect of Fe content on the material's structure, surface chemistry, and electrocatalytic activity toward the oxygen reduction reaction (ORR). The increase of iron content led to a specific surface area decrease, preserving the morphological structure, with the formation of highly‐active catalytic sites, as indicated by X‐ray photoelectron spectroscopy (XPS) analysis. The rotating ring disk electrode experiments, performed at pH=13, confirmed the high ORR activity of both 0.5 Fe (E1/2=0.84 V) and 1.3 Fe (E1/2=0.83 V) catalysts, which were assembled at the cathode of a H2‐fed anion exchange membrane fuel cells (AEMFC) equipped with a FAA‐3‐50 membrane, evidencing promising performance (0.5 Fe, maximum power density, Max PD=69 mA cm−2 and 1.3 Fe, Max PD=87 mA cm−2) with further advancement prospects. More or less: A sustainable soft templating strategy allowed preparing highly porous Fe−N−C catalysts with different Fe contents. The effect of Fe content on the material's structure and electrocatalytic activity toward the oxygen reduction reaction (ORR) was elucidated. The formation of high‐active nitrogen‐ and iron‐based functional groups endowed electrocatalysts with excellent ORR activity.

Composite chitosan/phosphotungstic acid (CS/PTA) with the addition of TiO2 and Al2O3 particles were synthesized to be used as proton exchange membranes in direct methanol fuel cells (DMFCs). The influence of fillers was assessed through X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, liquid uptake, ion exchange capacity and methanol permeability measurements. The addition of TiO2 particles into proton exchange membranes led to an increase in crystallinity and a decrease in liquid uptake and methanol permeability with respect to pristine CS/PTA membranes, whilst the effect of the introduction of Al2O3 particles on the characteristics of membranes is almost the opposite. Membranes were successfully tested as proton conductors in a single module DMFC of 1 cm2 as active area, operating at 50 °C fed with 2 M methanol aqueous solution at the anode and oxygen at the cathode. Highest performance was reached by using a membrane with TiO2 (5 wt.%) particles, i.e., a power density of 40 mW cm−2, almost doubling the performance reached by using pristine CS/PTA membrane (i.e., 24 mW cm−2).

The use of Cs0.5H0.5PW12O40 insoluble salt as a superacid promoter in the catalyst layer of a polymer electrolyte membrane fuel cell (PEMFC) has been investigated. An increase of performance has been recorded at intermediate temperatures (110–130 °C) and under low relative humidity (R.H.). The promoter appears to mitigate the ionomer dry-out effects in the catalytic layer and produces an increase of the extent of the catalyst-electrolyte interface as demonstrated by cyclic voltammetry analysis. These effects are also corroborated by a significant decrease of polarization resistance at intermediate temperatures. Such characteristics have been demonstrated for a conventional membrane-electrode assembly based on a Pt-Co alloy and a Nafion 115 membrane.

AEMFC is an attractive alternative to PEMFCs, due to the faster reaction kinetics that permits to use non‐platinum‐group metal catalysts and thanks to the high pH of the electrolyte allows less expensive metal hardware. In any case, the use of an alkaline exchange polymeric membrane as an electrolyte requires the development and optimization of the electrode structures and MEA. In this work, MEAs, based on FAA3‐50 commercial membrane, were developed and electrochemically characterized in single cell configuration. The hydroxylic exchange procedure of membrane and ionomer, was evaluated. The influence of different electrochemical activation procedures, and the presence of a microporous layer (MPL) in the electrodic structure were assessed. The developed MEAs were electrochemically characterized in a 25 cm2 single cell at different operative conditions. A maximum power density of 140 mW cm−2 at 60 °C was reached with the optimized MEAs. Polymer Electrolyte for Anion Exchange Membrane Fuel Cells: Enhancing performance by optimising electrochemical conditioning, electronic structure and anion exchange time.

This paper describes the use of a commercial Fumasep® FAA3-50 membrane as an anion exchange membrane (AEM) in alkaline direct methanol fuel cells (ADMFCs). The membrane, supplied in bromide form, is first exchanged in chloride and successively in the hydroxide form. Anionic conductivity measurements are carried out in both a KOH aqueous solution and in a KOH/methanol mixture. AEM-DMFC tests are performed by feeding 1 M methanol, with or without 1 M KOH as a supporting electrolyte. A maximum power density of 5.2 mW cm−2 at 60 °C and 33.2 mW cm−2 at 80 °C is reached in KOH-free feeding and in the alkaline mixture, respectively. These values are in good agreement with some results in the literature obtained with similar experimental conditions but with different anion exchange membranes (AEMs). Finally, methanol crossover is investigated and corresponds to a maximum value of 1.45 × 10−8 mol s−1 cm−2 at 50 °C in a 1 M KOH methanol solution, thus indicating that the Fumasep® FAA3-50 membrane in OH form is a good candidate for ADMFC application.

A series of quaternary ammonium-functionalized polysulfones were successfully synthesized using a chloromethylation two-step method. In particular, triethylammonium and trimethylammonium polysulfone derivatives with different functionalization degrees from 60% to 150% were investigated. NMR spectroscopic techniques were used to determine the degree of functionalization of the polymers. The possibility to predict the functionalization degree by a reaction tool based on a linear regression was highlighted. Anionic membranes with a good homogeneity of thickness were prepared using a doctor-blade casting method of functionalized polymers. The chemical–physical data showed that ion exchange capacity, water content, and wettability increase with the increase of functionalization degree. A higher wettability was found for membranes prepared by the trimethylamine (TMA) quaternary ammonium group. A degree of functionalization of 100% was chosen for an electrochemical test as the best compromise between chemical–physical properties and mechanical stability. From anionic conductivity measurement a better stability was found for the triethylamine (TEA)-based membrane due to a lower swelling effect. A power density of about 300 mW/cm2 for the TEA-based sample at 60 °C in a H2/O2 fuel cell was found.

CeO2 nanoparticles were coated with polydopamine (PDA) by dopamine polymerization in water dispersions of CeO2 and characterized by Infrared and Near Edge X-ray Absorption Fine Structure spectroscopy, Transmission Electron Microscopy, Thermogravimetric analysis and X-ray diffraction. The resulting materials (PDAx@CeO2, with x = PDA wt% = 10, 25, 50) were employed as fillers of composite proton exchange membranes with Aquivion 830 as ionomer, to reduce the ionomer chemical degradation due to hydroxyl and hydroperoxyl radicals. Membranes, loaded with 3 and 5 wt% PDAx@CeO2, were prepared by solution casting and characterized by conductivity measurements at 80 and 110 °C, with relative humidity ranging from 50 to 90%, by accelerated ex situ degradation tests with the Fenton reagent, as well as by in situ open circuit voltage stress tests. In comparison with bare CeO2, the PDA coated filler mitigates the conductivity drop occurring at increasing CeO2 loading especially at 110 °C and 50% relative humidity but does not alter the radical scavenger efficiency of bare CeO2 for loadings up to 4 wt%. Fluoride emission rate data arising from the composite membrane degradation are in agreement with the corresponding changes in membrane mass and conductivity.

Perfluorinated sulfonic acid (PFSA) polymers such as Nafion® are widely used for both electrolyte membranes and ionomers in the catalytic layer of membrane-electrode assemblies (MEAs) because of their high protonic conductivity, σH, as well as chemical and thermal stability. The use of PFSA polymers with shorter side chains and lower equivalent weight (EW) than Nafion®, such as Aquivion® PFSA ionomers, is a valid approach to improve fuel cell performance and stability under drastic operative conditions such as those related to automotive applications. In this context, it is necessary to optimize the composition of the catalytic ink, according to the different ionomer characteristics. In this work, the influence of the ionomer amount in the catalytic layer was studied, considering the dispersing agent used to prepare the electrode (water or ethanol). Electrochemical studies were carried out in a single cell in the presence of H2-air, at intermediate temperatures (80–95 °C), low pressure, and reduced humidity ((50% RH). %). The best fuel cell performance was found for 26 wt.% Aquivion® at the electrodes using ethanol for the ink preparation, associated to a maximum catalyst utilization.