The development of active hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) catalysts for use in anion exchange membrane fuel cells (AEMFCs), which are free from platinum group metals (PGMs), is expected to bring this technology one step closer to commercial applications. This paper reports our recent progress developing HOR Pt-free and PGM-free catalysts (Pd/CeO₂ and NiCo/C, respectively), and ORR PGM-free Co₃O₄ for AEMFCs. The catalysts were prepared by different synthesis techniques and characterized by both physical-chemical and electrochemical methods. A hydrothermally synthesized Co₃O₄ + C composite ORR catalyst used in combination with Pt/C as HOR catalyst shows good H₂/O₂ AEMFC performance (peak power density of ~388 mW cm⁻²), while the same catalyst coupled with our flame spray pyrolysis synthesised Pd/CeO₂ anode catalysts reaches peak power densities of ~309 mW cm⁻². Changing the anode to nanostructured NiCo/C catalyst, the performance is significantly reduced. This study confirms previous conclusions, that is indeed possible to develop high performing AEMFCs free from Pt; however, the challenge to achieve completely PGM-free AEMFCs still remains.

Gas diffusion layers (GDLs) play a critical role in anion exchange membrane fuel cell (AEMFC) water management. In this work, the effect of GDL thickness on the cell performance of the AEMFC was experimentally investigated. Three GDLs with different thicknesses of 120, 260, and 310 µm (denoted as GDL-120, GDL-260, and GDL-310, respectively) were prepared and tested in a single H₂/O₂ AEMFC. The experimental results showed that the GDL-260 employed in both anode and cathode electrodes exhibited the best cell performance. There was a small difference in cell performance for GDL-260 and GDL-310, while water flooding was observed in the case of using GDL-120 operated at current densities greater than 1100 mA cm⁻². In addition, it was found that the GDL thickness had more sensitivity to the AEMFC performance as used in the anode electrode rather than in the cathode electrode, indicating that water removal at the anode was more challenging than water supply at the cathode. The strategy of water management in the anode should be different from that in the cathode. These findings can provide a further understanding of the role of GDLs in the water management of AEMFCs.

The performance of an anion exchange membrane fuel cell (AEMFC) under various operating conditions, including cell temperature and humidification of inlet gases, was systematically investigated in this study. The experimental results indicate that the power density of an AEMFC is susceptible to the cell temperature and inlet gas humidification. A high performance AEMFC can be achieved by elevating the cell operating temperature along with the optimization of the gas feed dew points at the anode and cathode. As excess inlet gas humidification at the anode is supplied, the flooding is less severe at a higher cell temperature because the water transport in the gas diffusion substrate by evaporation is more effective upon operation at a higher cell temperature. The cell performance is slightly affected when the humidification at the anode is inadequate, owing to dehydration of the membrane, especially at a higher cell temperature. Furthermore, the cell performance in conditions of under-humidification or over-humidification at the cathode is greatly reduced at the different cell temperatures tested due to the dehydration of the anion exchange membrane and the water shortage or oxygen mass transport limitations, respectively, for the oxygen reduction reaction. In addition, back diffusion could partly support the water demand at the cathode once a water concentration gradient between the anode and cathode is formed. These results, in which sophisticated water management was achieved, can provide useful information regarding the development of high-performance AEMFC systems.