Highly loaded carbon black supported Pt catalysts for fuel cells.

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]