Nanostructured bimetallic alloys prepared via mechanochemical synthesis as PEMFC electrocatalysts for automotive applications

Abstract

Pt-Co alloys prepared by high energy ball milling synthesis were tested as electrocatalysts for hydrogen fueled Polymer Electrolyte Membrane Fuel Cells (PEMFC). In the present contribution we report on the first results regarding the electrochemical behaviour of two samples of Pt-Co alloys. One sample contains 20 wt.% alloy Pt:Co in the molar ratio 0.25:0.75 and C 80 wt.% and the second one Pt:Co in the molar ratio 0.75:0.25 and C 80 wt.%. The electrochemically active surface (EAS) was determined by cyclic voltammetry data while the electrocatalyst performance in a real cell was obtained by assembling Membrane Electrode Assemblies (MEAs) with the considered sample at the cathode. The results obtained, though indicating a lower performance than all-Pt catalysts, are quite interesting as they point out the importance of the C/Pt, Nafion/Pt and Pt/Co ratios that exert a deep influence onto the cell performance.

Relevant Parameters for the Mechanochemical Synthesis of Bimetallic Supported Catalysts

“…Metal co-deposition is relatively easy with the appropriate conditions, but the formation of an alloy usually requires subsequent thermal treatments [13,20,21,23]. Interestingly, it has been found that energy-intensive thermal steps can be overcome by longer milling times [11,14,24], even if this can lead to the contamination of the catalyst by the milling media. Regarding catalytic properties, the improvement of performance in terms of the activity, stability, and/or selectivity of bimetallic milled catalysts compared to analogous formulations obtained via other synthesis methods is widely reported.…”