Abstract
Carbon-supported bimetallic Pt-Co cathode catalysts have been previously identified as higher activity alternatives to conventional Pt/C catalysts for fuel cells. In this work, a series of Pt-Co/C catalysts were synthesized using electroless deposition (ED) of Pt on a Co/C catalyst prepared by modified charge enhanced dry impregnation. X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM) characterization of the base catalyst showed highly dispersed particles. A basic ED bath containing PtCl62− as the Pt precursor, dimethylamine borane as reducing agent, and ethylenediamine as stabilizing agent successfully targeted deposition of Pt on Co particles. Simultaneous action of galvanic displacement and ED resulted in Pt-Co alloy formation observed in XRD and energy dispersive X-ray spectroscopy (XEDS) mapping. In addition, fast deposition kinetics resulted in hollow shell Pt-Co alloy particles while particles with Pt-rich shell and Co-rich cores formed with controlled Pt deposition. Electrochemical evaluation of the Pt-Co/C catalysts showed lower active surface but much higher mass and surface activities for oxygen reduction reaction compared to a commercial Pt/C fuel cell catalyst.
Highlights
Successful commercial adaptation of fuel cells is very much reliant on the economic viability of this technology
Temperature programmed analyses of the cobalt-impregnated carbon were done on the sample with 5.0 wt % Carbon Supported Cobalt (Co/C) loading to increase the concentration of products to be detected by the thermal conductivity detector (TCD)
A series of carbon-supported Pt-Co bimetallic catalysts were prepared by electroless deposition (ED) of Pt on a Co base catalyst
Summary
Successful commercial adaptation of fuel cells is very much reliant on the economic viability of this technology. Proton exchange fuel cells (PEMFCs) are highly considered for wide scale use in small form factor applications such as vehicles and mobile technology owing to their high performance and compact design. One of the most widely used catalysts for electrochemical (i.e., oxygen reduction reaction, ORR) applications is a carbon-supported platinum catalyst (Pt/C). Increasing catalyst activity can be done by synthesizing smaller particle sizes to achieve greater metal dispersion, where dispersion is defined as the fraction of the metal atoms exposed on the surface. Various methods have been developed to increase metal dispersion specially for Pt/C catalysts, there are arguments against smaller Pt particles in ORR catalysts as some studies have pointed to lower specific activity for highly dispersed (50%–100%) platinum for Catalysts 2016, 6, 83; doi:10.3390/catal6060083 www.mdpi.com/journal/catalysts
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