A 3D porous nitrogen-doped carbon-nanofiber-supported palladium composite as an efficient catalytic cathode for lithium–oxygen batteries
Palladium/porous nitrogen-doped carbon-nanofiber (Pd/PNCNF) composites with a three-dimensional (3D) network structure have been prepared by decorating Pd nanoparticles onto PNCNFs, which were derived from KOH activated polypyrrole nanofibers. The Pd nanoparticles decorated on the walls of the PNCNFs as a bifunctional catalyst play a key role in the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER), as evidenced by the electrochemical results in aqueous solution. With the synergistic effects from the PNCNF matrix with a highly conductive porous structure and the Pd nanoparticles with high electrocatalytic performance, a Li–O2 cell containing the Pd/PNCNF composite catalyst with 25 wt% Pd nanoparticles showed notably improved electrocatalytic performance compared to a cell containing its pure PNCNF counterpart, with higher capacities, lower overpotentials, and better cycling stability. Therefore, the Pd/PNCNF composite is proposed as a potential cathode catalyst for Li–O2 batteries.