Migration and Precipitation of Platinum in Anion‐Exchange Membrane Fuel Cells

Abstract

Despite the recent progress in increasing the power generation of Anion‐exchange membrane fuel cells (AEMFCs), their durability is still far lower than that of Proton exchange membrane fuel cells (PEMFCs). Using the complementary techniques of X‐ray micro‐computed tomography (CT), Scanning Electron Microscopy (SEM) and Energy Dispersive X‐ray (EDX) spectroscopy, we have identified Pt ion migration as an important factor to explain the decay in performance of AEMFCs. In alkaline media Pt+2 ions are easily formed which then either undergo dissolution into the carbon support or migrate to the membrane. In contrast to PEMFCs, where hydrogen cross over reduces the ions forming a vertical “Pt line” within the membrane, the ions in the AEM are trapped by charged groups within the membrane, leading to disintegration of the membrane and failure. Diffusion of the metal components is still observed when the Pt/C of the cathode is substituted with a FeCo−N−C catalyst, but in this case the Fe and Co ions are not trapped within the membrane, but rather migrate into the anode, thereby increasing the stability of the membrane.

Elucidating the degradation mechanisms of Pt-free anode anion-exchange membrane fuel cells after durability testing

“…The Pt migration may be attributed to the movement of Pt(OH) 2 (ref. 67 and 68) or Pt(OH) 4 2− species, following the electroosmotic flow of OH − from cathode to anode in accordance with Pourbaix diagram. 69,70 This is in line with significantly decreased ECSA and increased resistance of the Pt/C cathode after 500 h (ESI Fig.…”

Bioadhesive-Inspired Ionomer for Membrane Electrode Assembly Interface Reinforcement in Fuel Cells

“…51 It is known that the periodic "water flooding", together with other complex ever-changing physicochemical factors, including mechanical stress, fuel gas impulse, electrochemical reactions, and heat interchange, jointly corrupt the microstructure of the CLs, hence dramatically degrading the long-term stability of the AEMFC. 52,53 For CGMEA-10%, encouragingly, the voltage sags incurred by "water flooding" have been greatly alleviated and the cell voltage deterioration is negligible throughout 300 h (with a light voltage reduction rate of 0.03 mV h −1 ). A comparison of AEMFC single-cell performance and durability of the poly(arylene piperidinium)-based ionomers indicates that CGMEA-10% is a promising configuration for long-term operation (Figure S12 and Table S2).…”