PT AND PTCO ELECTROCATALYSTS PREPARED BY MECHANICAL ALLOYING AND METAL ORGANIC CHEMICAL VAPOUR DEPOSITION FOR THE OXYGEN REDUCTION REACTION IN ALKALINE MEDIA

摘要

Pt and Pt-Co (70-30) Electrocatalysts were obtained by Mechanical alloying (MA) of Pt and cobalt powders. They also were prepared as thin films on glassy carbon by chemical vapour deposition CVD of metal organic precursors of Pt and Co. The MA electrocatalysts consisted of agglomerated particles constituted of 20-25 nm crystallites. The CVD films had about 250 nm of thickness and the particles size was about 30 nm for Pt particles and 19 nm for Pt-Co particles. Some iron was determined by EDX 0.9% in Pt and 3.1% in Pt-Co for the samples prepared by MA. Tafel plots were performed for the elecrocatalysts obtained by both techniques, and the kinetic parameters for the ORR were determined. The results showed that PtCo alloys obtained by both techniques have higher exchange current densities than Pt prepared in the same conditions. The difference is higher for the materials prepared by MA. The Koutecky-Levich plots were compared with 2 and 4 electron pathways for the ORR: The MA and CVD obtained electrocatalysts showed a 4 electron transfer for the ORR.