Synergistic electro-catalysis of core/shell Pd/PdO nanoparticles and Cr(III)-doped NiCo2O4 nanofibers in aprotic Li-O2 batteries

In this work we discuss the co-catalysis in aprotic Li-O2 batteries of C-free nanostructured mixed oxide electrodes decorated by Pd/PdO core/shell nanoparticles. A Cr(III) doped NiCo2O4 material has been grown hydrothermally on an open Ni-mesh. Palladium nanoparticles have been synthesized by pulsed lased ablation in liquid acetone in the fs regime and deposited by drop casting onto the surface of the nanostructured mixed oxide electrodes. The resulting electrodes have been calcined at 300°C. The use of laser techniques to produce nanoparticles for aLOBs is here proposed for the first time in the literature, as well as the peculiar combination of Pd/PdO nanoparticles deposited onto C-free Cr(III) doped NiCo2O4 self-standing electrodes. Performance in aprotic Li-O2 batteries have been recorded in galvanostatic conditions and post mortem analysis of the electrode surfaces have been carried out by X-ray photoemission spectroscopy. The use of Pd/PdO nanoparticles as co-catalysts enhances the reversibility of the electrochemical oxygen reduction/evolution reactions. This beneficial effect originates by the decrease of the mean overvoltages compared to the bare Cr(III) doped NiCo2O4 electrodes, and extends the cell calendar life from 16 to 41 fully reversible galvanostatic cycles at J = 0.2 mAcm−2 with capacity limitation of 0.2 mAhcm−2.