Alkaline Membrane Fuel Cell Performance Research Articles

Investigating the Impact of the Ionomer on Alkaline Membrane Fuel Cell (AEMFC) Electrode Performance

AEMFCs as an alternative to proton exchange membrane fuel cell (PFMFC) have gained significant attention due to a lower corrosion environment and good activity with platinum group metal-free (PGM-free) catalysts.1 Extensive research has being performed in improving polymers for AEMFCs and have achieved dramatic improvements with novel polymer membranes and ionomer.2 Recent studies have demonstrated more than 3 W/cm2 fuel cell performance and over 2000h durability.3,4 However, few studies have focused on electrode ionomer even though the electrodes have been the primary components responsible for performance and durability improvements. The work that has been done hasn’t specifically focused on different ionomers and catalysts to probe the impact of ionomer on AEMFC performance and durability. In part, this has been due to limited materials availability to the research community, at NREL we have the benefit of access to a great materials library and various processing techniques that allows us to investigate this space.In this work, we investigate ionomer/catalyst interactions by tuning different ionomers, processing conditions and multiple catalysts. We have used these experiments to explore the role of electrodes on water management in the cells and water transport resistance in the electrodes. Additionally, we have applied in-situ and ex-situ electrochemical measurement methods to evaluate ion transfer resistance in the electrodes. These experiments can be correlated with observed performance and durability, and help build a relationship between electrode properties and observed device performance. These efforts help establish practical methods to explore electrode processing conditions that optimize cell performance and isolate factors that impact performance and durability. Reference: Gottesfeld, S.; Dekel, D. R.; Page, M.; Bae, C.; Yan, Y.; Zelenay, P.; Kim, Y. S. Journal of Power Sources 2018, 375, 170-184.Wang, J.; Zhao, Y.; Setzler, B. P.; Rojas-Carbonell, S.; Ben Yehuda, C.; Amel, A.; Page, M.; Wang, L.; Hu, K.; Shi, L.; Gottesfeld, S.; Xu, B.; Yan, Y. Nature Energy 2019, 4, 392-398.Noor Ul Hassan, Mrinmay Mandal, Garrett Huang, Horie Adabi Firouzjaie, Paul A Kohl, William E Mustain, Adv. Energy Mater. 2020, 10 2001986.Garrett Huang, Mrinmay Mandal, Xiong Peng, Ami C Yang-Neyerlin, Bryan S Pivovar, William E Mustain, Paul A Kohl, Journal of The Electrochemical Society, 166 (10) F637-F644 (2019)

Investigation on Preparation Conditions for High Performance MEA of Alkaline Membrane Fuel Cells

Recently, AMFCs (Alkaline Membrane Fuel Cell) using non-platinum group metal (PGM) based catalysts and having good efficiency have attracted attention as an alternative to PEMFCs. However, in spite of these important advantages, the development of materials for AMFC is still an important issue because the AMFC performance based on the platinum catalyst is still superior to that of non-PGM in an alkaline environment. [1]We here present various preparation methods of a membrane electrode assembly (MEA) in order to increase the performance of AMFCs. Kinds of the gas diffusion layer, solvents for catalyst slurry, commercial binders for electrodes, and PGM-free catalyst were the main parameters of MEA performance. For the exact comparison of each parameter, reference MEA was selected by the use of commercial parts such as 39BC (SIGRACET), Fumion membranes, and binders (FuMA-Tech Inc.,), Pt/C and PtRu/C (Tanaka Kikinzoku Kogyo K.K.). The cell test was performed at 70 °C and 100% RH with 1 L/min H2/O2 to both anode/cathode, respectively.As a result, the FAA-3-50 membrane with PGM catalyst layers showed excellent performance of over 1,000 mA/cm2 at 0.6 V. In addition, the performance of the PGM-free cathode catalyst was over 450 mA/cm2, which showed a possibility to non-PGM AMFCs. We observed the I-V curve, electrochemical surface area, linear sweep voltammograms, and ohmic resistance. Experimental conditions and results will be presented in detail.

Ultrafine Pt cluster and RuO2 heterojunction anode catalysts designed for ultra-low Pt-loading anion exchange membrane fuel cells

Pt–RuO2 heterojunction catalysts with a unique morphology show excellent alkaline membrane fuel cell performance at an ultra-low loading Pt anode.

How does a small structural change of anode ionomer make a big difference in alkaline membrane fuel cell performance?

Small changes in anode ionomeric binder structure may bring significant performance and durability improvement of anion-exchange membrane fuel cells.

Why Pt-Ru Catalyst Works Better for Alkaline Hydrogen Oxidation Reaction?

It is well-known that Pt-Ru alloy electrocatalysts perform better than Pt catalyst for the anode reaction in alkaline membrane fuel cells.1 However, it is unclear why Pt-Ru alloy catalyst performs better in alkaline membrane fuel cells. Strmcnik et al. suggested that the higher activity of Pt-Ru catalyst is due to increased oxophilicity of Pt catalyst by adding Ru component.2 Others suggested that the Ru component weakens the Pt-Had binding energy to improve hydrogen oxidation reaction.3,4 In this presentation, we demonstrate that the improved alkaline hydrogen oxidation reaction is due to the low benzene group adsorption on the catalyst surface when the Ru component is added to Pt. In order to support our hypothesis, we first compared the voltammograms of hydrogen oxidation reaction of commercial Pt and Pt-Ru alloy catalysts in 0.1 M benzyl ammonium hydroxide and tetramethyl ammonium hydroxide solutions.5 These experiments showed that the hydrogen oxidation reaction of Pt in the benzyl ammonium hydroxide solution is much slower than that of Pt in the tetramethyl ammonium hydroxide solution. More importantly, the hydrogen oxidation reaction in the benzyl ammonium hydroxide solution can be substantially increased when Pt-Ru alloy catalyst was used. Density functional theory calculations indicate that the adsorption of benzyl ammonium on the bimetallic catalyst is endergonic for all configurations of the benzyl ammonium cation, which explains the significantly better hydrogen oxidation reaction activity observed for the bimetallic catalyst. The adverse impact of benzene adsorption on electrocatalysts is further investigated in the fuel cell performance test. For this experiment, we decoupled the benzene adsorption effect from mechanistic alkaline HOR perspectives by measuring both acid and alkaline membrane fuel cell performance using polyaromatic and benzene-free perfluorinated ionomers. Both acid and alkaline fuel cells, we observed substantially better kinetic performance when Pt-Ru electrocatalyst was used with polyaromatic electrolytes. In stark contrast, Pt electrocatalyst showed better kinetic performance when benzene-free perfluorinated electrolyte was used. This indicates that the performance improvement using Pt-Ru catalyst in alkaline (and acid) conditions is not originated from the mechanistically slow hydrogen oxidation under alkaline environment but originated from the less benzene group adsorbing characteristics of Pt-Ru catalyst. Acknowledgement This work is supported by the US Department of Energy, Energy Efficiency and Renewable Energy, Fuel Cell Technology Office (Program Manager Dr. David Peterson).

Toward Improved Alkaline Membrane Fuel Cell Performance Using Quaternized Aryl-Ether Free Polyaromatics

Toward Improved Alkaline Membrane Fuel Cell Performance Using Quaternized Aryl-Ether Free Polyaromatics

Molecular Design Aspect of Anion Exchange Polymer Electrolytes

Anion exchange polymer electrolytes play an important role both in separator (membrane) and in electrode binder (ionomer). Depending on their role, polymer electrolytes must possess certain properties which are essential to improve the alkaline membrane fuel cell performance & durability. In this study, we will present molecular design aspects of anion exchange polymer electrolytes for the use of membranes and ionomeric binders. In-depth studies on chemical degradation of polyaromatic anion exchange membranes and importance of perfluoirnated structure in the catalyst layer will be discussed in addition to the effects of cation type on chemical degradation and interaction with electro-catalysis.

Backbone stability of quaternized polyaromatics for alkaline membrane fuel cells

The backbone stability of benzyl-trimethyl ammonium (BTMA) functionalized polyaromatics was investigated in two structurally differing polymer architectures; quaternized poly(arylene ether) (PAE) and poly(phenylene) (PP). FTIR analysis indicated the cleavage of aryl-ether linkages in quaternized PAEs under high pH environments, while no backbone degradation in quaternized PP was observed. The backbone degradation of PAEs not only significantly reduced the mechanical properties of the membranes, but also negatively impacted hydroxide conductivity. Membrane electrode assemblies (MEAs) using both PAE and PP membranes showed good initial alkaline membrane fuel cell performance. However, the PAE MEA displayed larger performance losses and failure after only 55h, due to a mechanical breach. No catastrophic failure of the PP MEA occurred after 300h, which further confirmed the stability of the polymer backbone.

Impact of Low Cathode Humidification on Alkaline Membrane Fuel Cell Performance

not Available.

H2/Air Alkaline Membrane Fuel Cell Performance and Durability Using Novel Anionexchange Materials (Ionomer and Membrane) and Nonplatinum Group Metal Cathode Catalysts

not Available.

H 2/air alkaline membrane fuel cell performance and durability, using novel ionomer and non-platinum group metal cathode catalyst

The development of H 2/air alkaline membrane fuel cells (AMFCs) enables the use of non-platinum group metal (PGM) catalysts which are intrinsically stable and have an activity similar to platinum in alkaline media for the oxygen reduction reaction (ORR). As opposed to PEMFCs, the research and development of these types of catalysts for AMFC has had little attention and even less has been given to the development of alkaline membranes and ionomers. Acta S.p.A. has developed recently new non-PGM ORR catalysts with activity higher than Pt in alkaline media. More importantly, a new anionic ionomer derived from cheap starting materials with optimum performance has been produced. In this paper we demonstrate the use of this new ionomer in H 2/air AMFCs showing the first polarization and durability data, with current densities higher than those recently reported in the literature. Furthermore, we report the effect of CO 2 on AMFC performance, showing the possibility of use of such alkaline devices not only in outer-space applications, but also with atmospheric air for large scale devices.

In-situ Observation of CO2 through the Self-purging in Alkaline Membrane Fuel Cell (AMFC)

Alkaline membrane fuel cell (AMFC) performance was investigated comparing clean air and ambient air as oxidizing gases. Maximum power density was 120 mW/cm2 in the case of ambient air, and it was below 1/2 of that obtained with clean air. By analyzing anode exhaust gas with FT-IR or mass spectroscopy, released CO2 through the self-purging was directly observed for the first time. In the case of clean air, almost all HCO3- counter anion was released at the higher current density, to make the AMFC performance better.