The major objectives of this study are to identify the best activation procedure between commonly used procedures that can significantly reduce the conditioning duration and to understand the change in interfacial properties during conditioning. In order to do that, three on‐line activation procedures were employed for activating of identical MEAs in PEMFC and studied by polarization curve and electrochemical impedance spectroscopy (EIS). These methods are constant current (0.25 A cm–2) for 19 h, constant voltage (0.6 V) for 9 h, and USFCC protocol.The best performance was achieved by USFCC protocol within 15 h, but by constant voltage procedure, 96% of mentioned protocol was obtained during 6 h. So constant voltage activation proceeded remarkably fast, and most of the activation process was achieved in the first few hours.Obtained results from Nyquist plots during/after MEA conditioning indicate mentioned process are irreversible and interfacial structures of MEAs are different even after finishing of MEA break‐in. It could be affected the MEA performance and even its durability. These results are consistence with the obtained performance of activated MEAs either in H2/air or H2/O2 PEMFC. We found the mentioned constant current procedure consume long time without reaching to expectable performance even after 19 h.
Due to the importance of low cost and e cient electrodes development for alkaline water electrolysis, optimization of Ni-Mo coated stainless steel is investigated in the work to use as the cathode of alkaline water electrolyser. The crystallographic structure and surface morphology and composition of the studied coatings is characterized by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM).The electrocatalytic activity for the Hydrogen evolution reaction (HER) is evaluated using electrochemical measurement. Also, optimization of electrodeposition bath is investigated to promote the catalytic activity for HER. The results show that Nickel-Molybdenum alloy exhibits better HER activity and at -1.7 V vs. Ag/AgCl, current density of 180 mA cm − 2 is achieved. Also, the cell analysis tests revealed that using optimized electrode, at current density of 1.5 A.cm − 2 and operating temperature of 60°C, the cell operates at 1.9 V that is compatible to use for large scale industrial alkaline water electrolysis units.
HighlightsCatalytic activity of Ni, Mo and Ni-Mo alloy coated stainless steel is compared in HER.Ni-Mo coated cathode is more active than Ni and Mo coatings for HER.The electrodeposition bath composition affected the catalytic activity of Ni-Mo alloy.Optimization of electrodeposition bath is led to the cathode active area and HER activity increase.
The cathode catalyst layer void volume of the proton exchange membrane fuel cell (PEMFC) determines the available three‐phase regions and routes of mass transfer in the membrane electrode assembly (MEA). In this paper, four MEAs with different void volume of cathode catalyst layer have been made and their performance was evaluated and analyzed. The results show that for the MEA with cathode catalyst layer porosity of 20.8%, an optimal structure and a proper balance between catalyst layer void volume and Nafion content is obtained. The optimal void volume caused that electrochemical surface area for the MEA with the optimal structure be 1.45 times higher than MEA having a porosity of 29.5% at the end of the long‐term cycles. On the other hand, the mass transfer resistance (Rmt) at the end of long‐term cycles for MEA with the optimal structure is 4.8 times less than the same MEA having a porosity of 15.9%. This fact makes that MEA with the cathode catalyst layer porosity of 20.8%, both in short and in the long‐term, has higher and more stable performance than other MEAs; so that its maximum output power density has changed only 0.8% during 200 cycles.
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