U.S. Army Research Laboratory, United States
pp. 83 - 86
Keywords: nano-materials, catalysts, alloy and de-alloy, ORR
Optimization of particle size and particle’s nano-structure at the atomic level can precisely and effectively tune catalytic properties of materials, and enabling enhancement in both catalytic activity and stability. We synthesized a highly active and durable Ag-Co catalyst by optimizing the catalyst nano-structures for realization of fast electron-transfer and ion-transfer. The particle size and nano-structures were imaged with a scanning electron microscope (SEM), and a transmission electron microscope (TEM), which are varying through different alloying and de-alloying processes. The structure and composition of the Ag-Co alloy were also analyzed with X-ray diffraction analysis (XRD) and energy-dispersive X-ray spectroscopy (EDS). The catalytic activity and stability for oxygen reduction reaction (ORR) in alkaline media were examined with electrochemical methods at a catalyst coated rotating disk electrode (RDE). The activity of the Ag-Co material with Co/Ag ratio at 0.10 (a/a) gives the best performance. Further enhancement of activity is achieved by addition of graphene nano-platelets (GNP) as a catalyst support, and followed a process of heat-treatment. In comparison with a commercially available Ag nano material (20 – 40 M), there is a 170 mV decrease in over-potential for ORR in oxygen saturated 0.1 M KOH solution.