A practical method for measuring the true hydroxide conductivity of anion exchange membranes

International audienc

A high-temperature anion-exchange membrane fuel cell

In the past few years, developments in anion exchange membranes (AEMs) have led to a significant increase in hydroxide conductivities, ultimately yielding striking improvements in the performance of anion exchange membrane fuel cells (AEMFCs) at low operating temperatures, usually at 40–80 °C. Aside from these remarkable achievements, the literature is void of any work on AEMFCs operated at temperatures above 100 °C, despite the consensus from various models remarking that working at higher cell temperatures may lead to many significant advantages. In this work, we present the first high-temperature AEMFC (HT-AEMFC) tested at 110 °C. The HT-AEMFC exhibits high performance, with a peak power density of 2.1 W cm−2 and a current density of as high as 574 mA cm−2 measured at 0.8 V. This initial work represents a significant landmark for the research and development of the fuel cell technology, opening a wide door for a new field of research we call hereafter, HT-AEMFCs

The Effect of Ambient Carbon Dioxide on Anion‐Exchange Membrane Fuel Cells

Over the past 10 years, there has been a surge of interest in anion‐exchange membrane fuel cells (AEMFCs) as a potentially lower cost alternative to proton‐exchange membrane fuel cells (PEMFCs). Recent work has shown that AEMFCs achieve nearly identical performance to that of state‐of‐the‐art PEMFCs; however, much of that data has been collected while feeding CO2‐free air or pure oxygen to the cathode. Usually, removing CO2 from the oxidant is done to avoid the detrimental effect of CO2 on AEMFC performance, through carbonation, whereby CO2 reacts with the OH− anions to form HCO3− and CO32−. In spite of the crucial importance of this topic for the future development and commercialization of AEMFCs, unfortunately there have been very few investigations devoted to this phenomenon and its effects. Much of the data available is widely spread out and there currently does not exist a resource that researchers in the field, or those looking to enter the field, can use as a reference text that explains the complex influence of CO2 and HCO3−/CO32− on all aspects of AEMFC performance. The purpose of this Review is to summarize the experimental and theoretical work reported to date on the effect of ambient CO2 on AEMFCs. This systematic Review aims to create a single comprehensive account of what is known regarding how CO2 behaves in AEMFCs, to date, as well as identify the most important areas for future work in this field

Effect of the Synthetic Method on the Properties of Ni-Based Hydrogen Oxidation Catalysts

The latest progress in alkaline anion-exchange membranes has led to the expectation that less costly catalysts than those of the platinum-group metals may be used in anion-exchange membrane fuel cell devices. In this work, we compare structural properties and the catalytic activity for the hydrogen-oxidation reaction (HOR) for carbon-supported nanoparticles of Ni, Ni3Co, Ni3Cu, and Ni3Fe, synthesized by chemical and solvothermal reduction of metal precursors. The catalysts are well dispersed on the carbon support, with particle diameter in the order of 10 nm, and covered by a layer of oxides and hydroxides. The activity for the HOR was assessed by voltammetry in hydrogen-saturated aqueous solutions of 0.1 mol dm–1 KOH. A substantial activation by potential cycling of the pristine catalysts synthesized by solvothermal reduction is necessary before these become active for the HOR; in situ Raman spectroscopy shows that after activation the surface of the Ni/C, Ni3Fe, and Ni3Co catalysts is fully reduced at 0 V, whereas the surface of the Ni3Cu catalyst is not. The activation procedure had a smaller but negative impact on the catalysts synthesized by chemical reduction. After activation, the exchange-current densities normalized with respect to the ECSA (electrochemically active surface area) were approximately independent of composition but relatively high compared to catalysts of larger particle diameter

Practical ex-Situ Technique To Measure the Chemical Stability of Anion-Exchange Membranes under Conditions Simulating the Fuel Cell Environment

Anion-exchange membrane (AEM) degradation during fuel cell operation represents the main challenge that hampers the implementation of AEM fuel cells (AEMFCs). Reported degradation values of AEMs are difficult to reproduce as no standard methods are used. The present use of different techniques based on exposure of membranes to aqueous KOH solutions under different conditions and measuring different outputs during time does not allow for a reliable and meaningful comparison of reported degradation data of different AEMs. In this study, we present a practical and reproducible ex-situ technique to measure AEM degradation in conditions that mimic an operando fuel cell environment. In this novel technique, we measure the change of the true hydroxide conductivity of the AEM over time, while exposing it to different relative humidity conditions. The technique does not make use of liquid alkaline solution, thus simulating real fuel cell conditions and providing a good baseline for comparative degradation studies