Search

Membrane electrode assemblies (MEAs) for anion exchange membrane fuel cells (AEMFCs) were manufactured from commercial materials: Pt/C catalyst, A201 AEM and AS4 ionomer by using an industrial mass-production digital printing method. The MEA designs selected are close to those recommended by US Department of Energy, including low loading of platinum on the cathode side (0.2 mg cm −2 ). Polarization curves and electrochemical impedance spectroscopy (EIS) were applied for MEA evaluation in fuel cell conditions with variation of gas humidification and oxygen partial pressure (air vs oxygen). The typical impedance curves recorded at H 2 /O 2 gas configuration consist of high- and medium-frequency arcs responsible for hydrogen oxidation and oxygen reduction, respectively. Operation with air as a cathode feed gas resulted in a decrease in AEMFC performance due to possible CO 2 poisoning and mass transfer losses. At the same time, EIS demonstrated formation of a low frequency loop due to diffusion limitations. Despite the low loading of platinum on the cathode (0.2 mg cm −2 ), a peak power density of ∼330 mW cm −2 was achieved (at 50/50% of RH on anode and cathode), which is substantially higher performance than for AEMFC MEAs tested at similar conditions. [ABSTRACT FROM AUTHOR]

A commercial high surface area carbon black (808 m 2 g −1 ), low surface area carbon black (226 m 2 g −1 ) and an experimental grade medium surface area carbon black (ExpCB, 384 m 2 g −1 ) were studied as supports for platinum deposition: (i) from true solutions of H 2 PtCl 6 , Pt(C 5 H 7 O 2 ) 2 , Pt(NH 3 ) 4 (NO 3 ) 2 , or Pt(NH 3 ) 2 (NO 2 ) 2 , and (ii) from fine slurries of Pt(C 5 H 7 O 2 ) 2 or PtO 2 to achieve high Pt loadings of 60 wt.%. Temperature programmed reduction (TPR) revealed that PtO 2 , H 2 PtCl 6 , Pt(C 5 H 7 O 2 ) 2 , Pt(NH 3 ) 4 (NO 3 ) 2 , and Pt(NH 3 ) 2 (NO 2 ) 2 deposited on carbon blacks were reduced to metallic Pt at 0, 70, 120, 140, 150 °C, respectively. Cyclic voltammetry (CV) was carried out on electrodes prepared from selected catalyst materials on a rotating-disc electrode (RDE). The electrochemically active surface area (ESA) of the platinum and electrocatalytic activities towards the oxygen-reduction reaction (ORR) were evaluated from the RDE measurements, in which also the stability towards electrochemical ageing was investigated. These analyses indicated that impregnation by H 2 PtCl 6 is the most suitable of the studied catalyst synthesis methods. Mass-specific ORR activities similar to that of commercial reference catalyst are obtained. Catalysts prepared on carbon ExpCB showed greater stability than those based on 350G. Further increase in stability results from dechlorination of the catalyst. [ABSTRACT FROM AUTHOR]

A new platinum group metal (PGM)-free proton exchange membrane fuel cell (PEMFC) cathode catalyst materials, synthesized using the VariPore™ method by Pajarito Powder, LLC, are characterized for their structure and activity. The physico-chemical analysis of the iron-nitrogen-carbon (Fe-N-C) electrocatalysts show mesoporous carbon material effectively doped with iron and nitrogen. The materials have an average pore size of 7–8 nm and high specific surface area. The Fe-N-C catalysts exhibit good oxygen reduction reaction (ORR) activity in 0.5 M H 2 SO 4 electrolyte with high half-wave potential and sustainable electrochemical stability over 10,000 repeated potential cycles with insignificant losses in their activities. As cathode catalysts in a PEMFC, the Fe-N-C materials deliver remarkably good fuel cell performance at low overpotential approaching that of the commercial Pt catalyst. The high ORR electrocatalytic activity of these Fe-N-C catalysts is credited to the synergy between nitrogen-moieties, specifically pyrrolic-N, pyridinic-N, and graphitic-N, and iron in addition to the high mesoporosity that facilitate an effective reaction path in boosting the electrocatalytic activity and stability. [Display omitted] • State-of-the-art commercial PGM-free catalysts for ORR were characterized and evaluated. • Was shown that active centres are atomically dispersed. • Performance of electrocatalysts was evaluated in industrially manufactured MEA form-factor. • The fuel cell performance is close to the state-of-the-art R&D PGM-free catalysts. [ABSTRACT FROM AUTHOR]