Highly loaded carbon black supported Pt catalysts for fuel cells

• Carbon black supports with surface area 226, 384 and 808 m2 g−1 compared.
• Deposition of PtO2, H2PtCl6, Pt(C5H7O2)2, Pt(NH3)4(NO3)2, and Pt(NH3)2(NO2)2.
• H2PtCl6 most suitable by H2 chemisorption and electrochemical RDE analysis.
• Dechlorination of the catalysts developed by NaOH and water washing.
• Better electrochemical stability of the carbon ExpCB with S(NE) = 384 m2 g−1.

A commercial high surface area carbon black (808 m2 g−1), low surface area carbon black (226 m2 g−1) and an experimental grade medium surface area carbon black (ExpCB, 384 m2 g−1) were studied as supports for platinum deposition: (i) from true solutions of H2PtCl6, Pt(C5H7O2)2, Pt(NH3)4(NO3)2, or Pt(NH3)2(NO2)2, and (ii) from fine slurries of Pt(C5H7O2)2 or PtO2 to achieve high Pt loadings of 60 wt.%. Temperature programmed reduction (TPR) revealed that PtO2, H2PtCl6, Pt(C5H7O2)2, Pt(NH3)4(NO3)2, and Pt(NH3)2(NO2)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 H2PtCl6 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.

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