Ultrafine PdMo alloy nanowires mitigate excessive oxygen adsorption to enhance oxygen reduction in Zn-air batteries

Palladium (Pd) is one of the most promising catalysts for oxygen reduction reaction (ORR), however its activity is limited by the excessively strong adsorption of oxygen-containing intermediates. Herein, a one-dimensional (1D) ultrafine PdMo alloy nanowire (PdMo NWs) is synthesized, which exhibits excellent ORR activity and stability in both half cells and zinc-air batteries. The mass activity (1.08mAμg_Pd^-1) and specific activity (1.74 mA cm^-2) of PdMo NWs are 9.2 and 6.9 times higher than that of a commercial nanosized Pt/C, respectively. Especially, the zinc-air battery with the PdMo NWs cathode achieves a peak power density of 214.8 mW cm^-2, and remains stable in a 160 h durability test. DFT calculations and in-situ electrochemical Fourier-transform infrared spectroscopy characterization reveal that the introduction of Mo significantly downshifts the d-band center of Pd, inhibiting excessive adsorption of the oxygen intermediates, thereby accelerating the ORR processes. This work demonstrates a 1D ultrafine Pd-based alloy nanowire as an effective and robust electrocatalyst for the ORR, and provides direct spectroscopic evidence for alleviated adsorption of oxygen intermediates on PdMo surfaces.