Platinum−Gold Nanoparticles: A Highly Active Bifunctional Electrocatalyst for Rechargeable Lithium−Air Batteries

PtAu nanoparticles (NPs) were shown to strongly enhance the kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in rechargeable Li−O₂ cells. Li−O₂ cells with PtAu/C were found to exhibit the highest round-trip efficiency reported to date. During ORR via xLi⁺ + O₂ + xe⁻ → Li_xO₂, the discharge voltage with PtAu/C was considerably higher than that of pure carbon and comparable to that of Au/C. During OER via Li_xO₂ → xLi⁺ + O₂ + xe⁻, the charge voltages with PtAu/C fell in the range from 3.4 to 3.8 V_Li, which is slightly lower than obtained with Pt. It is hypothesized that PtAu NPs exhibit bifunctional catalytic activity, having surface Au and Pt atoms primarily responsible for ORR and OER kinetics in Li−O₂ cells, respectively.