Abstract
Catalyst degradation results in performance losses of proton exchange membrane fuel cells (PEMFC) and is caused by electrochemical instability of commonly used platinum on carbon black (Pt/C). In this study, a comparison in durability of commercial Pt/C with a new Pt catalyst on a nanocomposite of fluorine-doped SnO2 (FTO) and reduced graphene oxide (rGO) is carried out. Transmission electron microscopy (TEM) shows similar Pt distributions on support surfaces and Pt particle sizes so that a high comparability of support materials during durability investigation is ensured. High resolution TEM with EDS reveals dispersed Pt anchored at FTO–rGO interfaces. During stripping voltammetry Pt/FTO–rGO provides weaker CO sorption than Pt/C, indicating higher CO tolerances. Accelerated stress testing (0.05–1.47 VRHE) provokes Pt degradation on both supports in comparable rates. However, the FTO–rGO nanocomposite presents the more stable substrate in this study compared to carbon black. Identical location TEM illustrates stable FTO particles in size and position on rGO surface. Moreover, unchanged hydroquinone/quinone (HQ/Q) amounts and double layer capacitance in case of Pt/FTO–rGO were revealed by cyclic voltammetry. On the contrary, standard Pt/C shows significantly more generation of HQ/Q functionalities by a factor of 25 and thus higher carbon corrosion.
Highlights
Proton exchange membrane fuel cells (PEMFCs) are attractive for stationary, automotive and portable applications, but proton exchange membrane fuel cells (PEMFC) still show a loss of performance during cell operation.[1,2,3] Chemical, electrochemical, physical, thermal and mechanical processes result in the aging of fuel cell components like catalyst and membrane.[2,4,5,6] Especially the fuel cell catalyst – commonly consisting of platinum supported on carbon black (Pt/C) – shows degradation under PEMFC conditions at low pH values and cell voltages up to 1.4 V during startstop operation.[7]
Transmission electron microscopy with energy-dispersive X-ray spectroscopy (EDS).—transmission electron microscopy (TEM) images are used to illustrate the progress in Pt/fluorine-doped tin (IV) oxide (FTO)–Reduced graphene oxide (rGO) catalyst production
We suggest that the detection of two CO signals for Pt/FTO–rGO in Figure 6a arise from Pt particles interacting with FTO (CO signal at 0.76 VRHE) and Pt particles not interacting with FTO (CO signal at 0.86 VRHE)
Summary
Catalyst synthesis.—The Pt catalyst on FTO–rGO is prepared in four steps. Firstly, a modified Hummers method[33] was used to chemically oxidize natural graphite (Graphit Kropfmuhl GmbH, Germany). In a typical synthesis of graphene oxide, 1.0 g of graphite was given into 25 mL concentrated sulfuric acid (Carl Roth GmbH und Co. KG, Germany) and sonicated. Ammonium hydroxide (28% NH3 in water, Alfa Aesar GmbH & Co KG, Germany) was dropwise added until the mixture achieved pH 8. To prepare the catalyst with 20 wt% Pt nanoparticles on FTO–rGO, 1.6 mL of the previously prepared platinum suspension was washed and centrifuged with 1 M HCl to remove ethylene glycol.[35] Pt particles and 16 mg FTO–rGO were mixed in acetone and sonicated until the solvent was evaporated and the final catalyst was remained. Physical characterization.—TEM samples were prepared by suspending the catalyst in ethanol and placing a drop on a polyvinylformal coated Cu grid (200 mesh, Plano GmbH, Germany). To observe catalyst degradation with the microscope the same grid position before and after AST can be investigated
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
