docSynchrotron SAXS and GISAXS characteriza?on of HT
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Synchrotron SAXS and GISAXS characteriza?on of HT
Synchrotron SAXS and GISAXS characteriza3on of HT-‐PEMFC catalyst degrada3on Francesco Valle1, Nicola Zuliani1, BenedeEa Marmiroli2, Heinz Amenitsch2, Rodolfo Taccani1 1 Engineering and Architecture Department, University of Trieste, Italy 2 Ins>tute of Inorganic Chemistry, Graz University of Technology EFC 2013, 10 December 2013 -‐ EF13120 Aim of the research 1 Test the suitability of SAXS for the catalyst characteriza3on in HT-‐PEMFCs. 2 Inves3gate the catalyst evolu3on due to poten3al cyclying in HT-‐PEMFCs and the influence of OCV during dynamic opera3on. commercial HT-‐MEAs have been used Francesco Valle, Università degli Studi di Trieste -‐ EF13120 2 Methodology 1 Development of a SAXS procedure to inves3gate the catalyst -‐ analysis of single components of a HT-‐PEM MEA -‐ first results 2 SAXS on aged samples -‐ development of a ADT test bench -‐ development of ADT protocols for HT-‐PEMFCs -‐ durability tests -‐ performance analysis -‐ SAXS analysis Francesco Valle, Università degli Studi di Trieste -‐ EF13120 3 Small Angle X-‐ray ScaEering SAXS is a scaEering technique based on the detec3on of electron density inhomogenei3es within the sample. → shape, structure and distribu3on of colloids. k’ 2θ k scattering pattern ∞ scaEering vector q = k’ – k 1 d Francesco Valle, Università degli Studi di Trieste -‐ EF13120 4 Small Angle X-‐ray ScaEering Integration of the image detected with respect to the scattering vector q image detected scattering pattern ↓ ScaEering Intensity Curve Francesco Valle, Università degli Studi di Trieste -‐ EF13120 5 Small Angle X-‐ray ScaEering Beamline setup at IONIZATION CHAMBER SAMPLE VACUUM TUBE DETECTOR BEAM SAMPLE SUPPORT BEAMSTOP WITH DIODE Francesco Valle, Università degli Studi di Trieste -‐ EF13120 6 Small Angle X-‐ray ScaEering Small-‐Angle ScaEering setups SAXS paEern rigaku.com GISAXS paEern aps.anl.gov Francesco Valle, Università degli Studi di Trieste -‐ EF13120 7 Small Angle X-‐ray ScaEering Model used to describe the Pt nanopar3cles system within the catalyst layer: -‐ s3cky hard-‐spheres -‐ inter-‐par3cle poten3al -‐ Shultz distribu3on of R -‐ generalized Porod law (carbon) → ScaEering Intensity CURVE FITTING with the experimental curve Francesco Valle, Università degli Studi di Trieste -‐ EF13120 8 Small Angle X-‐ray ScaEering Example of scaEering intensity curves Silver behenate monodisperse and ordered structure Francesco Valle, Università degli Studi di Trieste -‐ EF13120 MEA mul3-‐layer structure 9 Preliminary SAXS analysis ScaEering contribu3on of the different layers no contribu3on Pt par3cles into the GDL par3cles contribu3on is more marked without GDL lower scaEering contribu3on Francesco Valle, Università degli Studi di Trieste -‐ EF13120 10 Preliminary SAXS analysis ScaEering contribu3on of Vulcan XC-‐72 The informa3on of the Pt NPs is present only in the catalyst layer, as expected. Francesco Valle, Università degli Studi di Trieste -‐ EF13120 11 Accelerated Degrada3on Tests Test bench NI CompactRIO controller, LabVIEW environment → start-‐up/shut-‐down procedures → stand-‐alone opera3on → different opera3on modes → remote control → emergency protocols Francesco Valle, Università degli Studi di Trieste -‐ EF13120 12 Accelerated Degrada3on Tests Samples subjected to load cycling MEA a 100 h conditioning at 0.2 A/cm2 + 100,000 triangle load cycles of 16 s between 0.01 and 0.5 A/cm2. MEA b 100 h conditioning at 0.2 A/cm2 + OCV OCV 100,000 triangle load cycles of 16 s between 0 and 0.5 A/cm2. Francesco Valle, Università degli Studi di Trieste -‐ EF13120 13 Accelerated Degrada3on Tests Results for the samples subjected to load cycling MEA a < 25 mV loss at 0.6 A/cm2 MEA b < 30 mV loss at 0.6 A/cm2 OCV OCV Francesco Valle, Università degli Studi di Trieste -‐ EF13120 14 Accelerated Degrada3on Tests Results for the samples subjected to load cycling 3 points of exposi3on for each sample. Median value of R: Reference 2.26 nm 74% incr. 3.67 nm 102% incr. 3.83 nm Francesco Valle, Università degli Studi di Trieste -‐ EF13120 15 Ongoing ac3vi3es Grazing Incidence Small-‐Angle X-‐ray ScaEering (GISAXS) on the catalyst layer Limited beam penetra3on into the surface (few 102 nm deep) - analysis of the catalyst layer only - separation of the anode and cathode scattering Francesco Valle, Università degli Studi di Trieste -‐ EF13120 16 Ongoing ac3vi3es SAXS mapping The purpose is to obtain the spa3al distribu3on of the catalyst structural features on a wide area of the MEA. scan A 3200 exposi3ons on an area of 40x40 mm. scan B 1000 exposi3ons on an area of 20x10 mm. x x y y A procedure of mul3ple fimng is in phase of elabora3on. Francesco Valle, Università degli Studi di Trieste -‐ EF13120 17 Conclusions -‐ A SAXS procedure to inves3gate the catalyst NPs evolu3on in HT-‐PEMFCs has been developed -‐ The ADT procedures implemented caused a significant evolu3on of the catalyst NPs system, both in terms of NP size and distribu3on -‐ SAXS analysis confirms that OCV opera3on affects catalyst degrada3on (higher polydispersity and mean size) Francesco Valle, Università degli Studi di Trieste -‐ EF13120 18 Future ac3vi3es -‐ improve the analy3cal model -‐ fimng of the GISAXS intensity curves -‐ SAXS on samples subjected to start-‐stop -‐ development of a mul3ple fit procedure to analyze the experimental data of the MEA mapping -‐ in-‐situ experiment in order to monitor in real 3me the catalyst evolu3on during opera3on Francesco Valle, Università degli Studi di Trieste -‐ EF13120 19 Thank you for the aEen3on! Francesco Valle [email protected] ENESYSLAB Engineering and Architecture department University of Trieste Via A. Valerio 10 34127 Trieste
