Oxygen-Driven Reconstruction Activates Quasi-Single Pd Sites in Hollow PdAg Nanotubes for Zinc–Air and Fuel Cells

Here, a template-engaged galvanic replacement strategy is developed to construct hollow PdAg alloy nanotubes, where interfacial oxygen drives surface reconstruction and stabilizes quasi-single Pd active sites. The interplay of atomic-scale characterizations and theoretical calculations reveals that the oxygen-induced atomic rearrangement downshifts the Pd d -band center, optimizes the adsorption-desorption energetics of ORR intermediates, and lowers the energy barrier for * OH desorption. The optimized Pd 0.30 @Ag catalyst achieves an onset potential of 0.951 V and a half-wave potential of 0.868 V in alkaline media, surpassing commercial Pt/C even at an ultra-low Pd loading (3 wt.%). Furthermore, Pd 0.30 @Ag-based electrodes deliver outstanding performance in both zinc-air batteries (ZABs) and anion-exchange membrane fuel cells (AEMFCs), demonstrating high power densities, excellent cycling stability, and strong potential for scalable platinum-free energy conversion devices. This work provides a general strategy for engineering interface-confined active sites through surface reconstruction, offering new insights into the rational design of next-generation electrocatalysts.