Pt based PEMFC catalysts prepared from colloidal particle suspensions – a toolbox for model studies

Abstract

A colloidal synthesis approach is presented that allows systematic studies of the properties of supported proton exchange membrane fuel cell (PEMFC) catalysts. The applied synthesis route is based on the preparation of monodisperse nanoparticles in the absence of strong binding organic stabilizing agents. No temperature post-treatment of the catalyst is required rendering the synthesis route ideally suitable for comparative studies. We report work concerning a series of catalysts based on the same colloidal Pt nanoparticle (NP) suspension, but with different high surface area (HSA) carbon supports. It is shown that for the prepared catalysts the carbon support has no catalytic co-function, but carbon pre-treatment leads to enhanced sticking of the Pt NPs on the support. An unwanted side effect, however, is NP agglomeration during synthesis. By contrast, enhanced NP sticking without agglomeration can be accomplished by the addition of an ionomer to the NP suspension. The catalytic activity of the prepared catalysts for the oxygen reduction reaction is comparable to industrial catalysts and no influence of the particle size is found in the range of 2-5 nm.

In-Operando Anomalous Small-Angle X-Ray Scattering Investigation of Pt3Co Catalyst Degradation in Aqueous and Fuel Cell Environments

“…Speder et al have shown limitations of PSD analyses based on TEM alone, based on the fact that particle sizes might be over/underestimated due to the limited contrast between the nanoparticles and the support. 33 Therefore, also included in Figure 1 are the initial Pt and Co PSDs for the Pt 3 Co/C powder, as found using ASAXS, showing a mean diameter of 5.2 nm and 4.9 nm, respectively. A second catalyst was also used in this study: heat-treated 40 wt% Pt nanoparticles supported on an Akzo Nobel Ketjen EC300J (Pt/C) carbon black with an initial mean diameter of 5.0 nm, as determined through TEM, also prepared by JMFC.…”

Improved carbon nanostructures as a novel catalyst support in the cathode side of PEMFC: a critical review

“…Moreover, Sepeder and Kongkanand, et al [54,55] Ethylene glycol solutions that contained metal precursors were refluxed at an appropriate temperature to reduce the metal ions to their elemental forms, which was followed by deposition of these particles onto the carbon surface. Greater dispersion, greater speed and simplicity are the advantages of this method.…”

The colloidal tool-box approach for fuel cell catalysts: Systematic study of perfluorosulfonate-ionomer impregnation and Pt loading

“…We propose that this observation can be explained by the chemical properties of the carbon black materials. As previously demonstrated, using a colloidal synthesis approach the number of defect sites and surface oxide groups play a key role in achieving high Pt NP dispersion [18,46]. Ketjenblack EC-600JD and Vulcan XC72R might have more defect sites than Ketjenblack EC-300J due to the production process from Ketjenblack EC-600JD.…”

“…[18,29]. In order to test the influence of ionomer impregnation on the ORR activity, PFSI can be added to the carbon support or to the Pt NPs suspension [18].…”

“…Thus different catalysts are prepared using the same stock solution of Pt NPs, but various commercially available carbon materials. This "tool-box" approach has been used before in various applications [18][19][20][21][22][23]; the new element of the present study is that also Nafion was directly introduced in the synthesis procedure allowing us to systematically investigate the influence of Nafion impregnation on the Pt utilization and oxygen reduction reaction (ORR) activity. The electrochemical properties of the investigated catalysts are characterized in RDE measurements using the thin film approach [24,25].…”