Interfacial oxygen atom modification of a PdSn alloy to boost oxygen reduction in zinc-air batteries

Modifying the surface of a catalyst with heteroatoms can regulate the interfacial atomic valence state and adjust the charge distribution, which is promising for obtaining desirable platinum carbon catalyst (Pt/C)-matched oxygen reduction reaction (ORR) catalytic performance. Here, we developed an efficient method to access O-rich crystalline interfacial-exposed palladium-tin alloy (1 11) crystal surfaces [Pd3Sn (11 1)] for highly efficient ORR via direct reduction of Pd/Sn metal salt species that are well dispersed in a nitrogen, phosphorus-doped carbonaceous (NPC) substrate. In addition to the other materials, preembedded Pd/Sn metal salt species in NPC control the release of metal sources upon reduction in the liquid phase, resulting in the grafting of an asprepared PdSn alloy with many merits, such as efficient electron conduction, short-range crystallinity and increased crystal interface exposure. The presence of a considerable quantity of oxygen atoms at the interface of small-sized PdSn alloys on NPC substrates has been methodically verified by powder X-ray diffraction, highresolution transmission electron microscopy and X-ray photoelectron spectroscopy characterizations. The PdSn-O sample exhibited excellent ORR activity, achieving an onset potential of -0.99 V and a half-wave potential of -0.88 V at 1600 rpm in O2-saturated 1.0 M KOH. Density functional theory simulations of pure Pd, PdO, the PdSn alloy and PdSn-O suggest that interfacial oxygen atom modification is responsible for the significantly improved ORR activity. The assembled zinc-air battery provides a high specific power of 218.9 mW cm-2 and a specific capacity of 810.6 mAh g-Zn1. Our approach has the potential to stimulate the preparation of O-rich crystalline interfacial-exposed alloy compounds for other energy conversion applications.