Recent Insights on Catalyst Layers for Anion Exchange Membrane Fuel Cells

Abstract

Anion exchange membrane fuel cells (AEMFCs) performance have significantly improved in the last decade (>1 W cm−2), and is now comparable with that of proton exchange membrane fuel cells (PEMFCs). At high current densities, issues in the catalyst layer (CL, composed of catalyst and ionomer), like oxygen transfer, water balance, and microstructural evolution, play important roles in the performance. In addition, CLs for AEMFCs have different requirements than for PEMFCs, such as chemical/physical stability, reaction mechanism, and mass transfer, because of different conductive media and pH environment. The anion exchange ionomer (AEI), which is the soluble or dispersed analogue of the anion exchange membrane (AEM), is required for hydroxide transport in the CL and is normally handled separately with the electrocatalyst during the electrode fabrication process. The importance of the AEI–catalyst interface in maximizing the utilization of electrocatalyst and fuel/oxygen transfer process must be carefully investigated. This review briefly covers new concepts in the complex AEMFC catalyst layer, before a detailed discussion on advances in CLs based on the design of AEIs and electrocatalysts. The importance of the structure–function relationship is highlighted with the aim of directing the further development of CLs for high‐performance AEMFC.

Di-piperidinium-crosslinked poly(fluorenyl-co-terphenyl piperidinium)s for high-performance alkaline exchange membrane fuel cells

“…The two cells run stably for 265 h and 110 h, respectively, with low voltage decay rate of ∼50 μV h −1 . Notably, most state-of-the-art AEMFCs 3–8,16,23,30–36 exhibited PPD values <2 W cm −2 and high voltage decay rates >300 μV h −1 during durability testing. Very few of them can display simultaneously high PPDs (>2.5 W cm −2 ) in H 2 –O 2 (or >1.4 W cm −2 in H 2 –air) and low voltage decay rates below 100 μV h −1 , such as PTFE-reinforced PNB 36 (∼3.0 W cm −2 in H 2 –O 2 and a voltage decay rate of 15.36 μV h −1 ) and high-density polyethylene (∼2.3 W cm −2 in H 2 –O 2 and a voltage decay rate of 32 μV h −1 ) AEMs.…”

“…However, AEMFCs are faced with many inherent challenges related to alkaline conditions, particularly in terms of power density and durability. 5–9…”

Application of Molecular Catalysts for the Oxygen Reduction Reaction in Alkaline Fuel Cells

“…Although testing catalysts in electrochemical cells using techniques such as the RDE is an important milestone in the development of ORR catalysts, good performance in the RDE does not always translate well to good performance in fuel cells. The chemical environment and operating conditions of fuel cells are very different from those in liquid electrolyte solutions, and parameters such as ionomer distribution, the level of humidity, catalyst loading, temperature, and so forth are becoming crucial . For these reasons, it is important to bridge the gap between testing molecular catalysts only in electrochemical cells, as became the standard in this field, and testing in fuel cells where more realistic conclusions can be drawn.…”

Cathodic Electrodeposition of MOF Films Using Hydrogen Peroxide

“…[1] In particular, substrate supported MOF films for separation, catalysis, energy storage and electronics are of special interest. [2][3][4][5][6][7][8] Several methods for the synthesis of MOF films have been developed such as the layer-by-layer deposition, liquid phase epitaxy deposition, spin coating, gellayer synthesis, chemical vapor deposition and electrosynthesis. [9][10][11][12][13][14][15] But most of these methods are either complex and/ or time/energy-consuming.…”