Synergistic Electro-Catalysis of Pd/PdO Nanoparticles and Cr(III)-Doped NiCo₂O₄ Nanofibers in Aprotic Li-O₂ Batteries

Abstract

In this work we discuss the co-catalysis in aprotic Li-O 2 batteries of C-free nanostructured mixed oxide electrodes decorated by Pd/PdO core/shell nanoparticles. A Cr(III) doped NiCo 2 O 4 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 NiCo 2 O 4 self-standing electrodes. Performance in aprotic Li-O 2 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 NiCo 2 O 4 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 .

Transition Metal Carbide Core/Shell Nanoparticles by Ultra-Short Laser Ablation in Liquid

“…On the other hand, the ablation of molybdenum, that has higher redox potential [27] and higher enthalpy of formation for its oxides with respect to tantalum, allows the formation of nanoparticles that are non completely oxidized, as observed by XRD measurement. This behavior is confirmed by the results obtained by laser ablation in water of metals with high redox potential such as Pt and Pd, where metallic NPs with a lighter oxide shell have been obtained [39][40][41][42].…”

Pulsed Laser in Liquids Made Nanomaterials for Catalysis

“…The laser-made Pd–PdO nanoparticles were immobilized on a Ni–CoO 4 -based electrode before calcination for aprotic lithium–air battery applications. Electrodes that were modified by the laser-made Pd–PdO nanoparticles initially lowered overpotentials, but cycling stability remained elusive . We note that palladium is even scarcer than platinum and ergo does not ameliorate cost and abundance concerns.…”

“…Electrodes that were modified by the laser-made Pd−PdO nanoparticles initially lowered overpotentials, but cycling stability remained elusive. 209 We note that palladium is even scarcer than platinum 210 and ergo does not ameliorate cost and abundance concerns.…”

“…208 Mixed Pd−PdO nanoparticles were synthesized by Brutti and co-workers by ablating a Pd target in acetone, using 800 nm, 120 fs pulses. 209 The laser-made Pd−PdO nanoparticles were immobilized on a Ni−CoO 4 -based electrode before calcination for aprotic lithium−air battery applications. Electrodes that were modified by the laser-made Pd−PdO nanoparticles initially lowered overpotentials, but cycling stability remained elusive.…”

“…Mixed Pd–PdO nanoparticles were synthesized by Brutti and co-workers by ablating a Pd target in acetone, using 800 nm, 120 fs pulses . The laser-made Pd–PdO nanoparticles were immobilized on a Ni–CoO 4 -based electrode before calcination for aprotic lithium–air battery applications.…”