Electrocatalytic behaviour towards oxygen reduction reaction of carbon-supported PtxMyAuz (M = Ni, Cu, Co) binary and ternary catalysts

Abstract

Carbon-supported binary and ternary nanocatalysts based on Pt, Me (Me=Ni, Co, Cu) and Au were synthesized by a “water in oil” microemulsion method and characterized by atomic absorption spectrometry or energy dispersive spectroscopy, X-ray photoelectron spectroscopy, thermogravimetry, transmission electron microscopy, X-ray diffraction, and electrochemical methods. A comparative study of the oxygen reduction reaction on binary and ternary nanocatalysts has been performed. The catalytic activity and the selectivity of the nanocatalysts towards the ORR have been determined in O2-saturated 0.1M HClO4 electrolyte. For binary systems, it was shown that the addition of Ni and Co to Pt led to an improvement of the catalytic activity, whereas the addition of Cu was detrimental for the ORR. The higher activities were achieved for atomic ratios close to that of Pt3Me defined compounds with Pt7Ni3/C displaying the highest activity. The modification of binary catalysts with gold led to increase the activity in the case of systems containing Co and Cu, and led to maintain the activity in the case of Ni-containing catalysts. The order of initial activity is: Pt6Ni2Au2/C>Pt6Co2Au2/C>Pt6Cu2Au2/C. Aging tests have been carried out on ternary catalysts, showing that a part of activity loss was due to gold segregation from the bulk to the surface of nanoparticles. After aging study for 1000 potential cycles between 0.6 and 1.05V vs. RHE in O2-saturated electrolyte, the order of activity was: Pt6Cu2Au2/C>Pt6Co2Au2/C>Pt6Ni2Au2/C.