Single-atom palladium on nonstoichiometric tungsten oxide as bifunctional electrocatalyst for zinc-air battery.

• Single-atom Pd/WO 2.72 is first prepared and used as a bifunctional electrocatalyst. • Pd atom is anchored to O atom in WO 2.72 to form stable single-atom structure. • The 5 %Pd/WO 2.72 shows excellent bifunctional electrocatalytic behaviors. • The assembled 5 %Pd/WO 2.72 zinc-air battery has good electrocatalytic performances. Searching for an excellent bifunctional electrocatalyst used in zinc-air batteries (ZABs) is a long-term and challenging task. Single-atom catalysts have been becoming potential bifunctional electrocatalysts because of their maximum metal atom utilization and low content of metal itself. Herein, noble metal palladium (Pd) is uniformly anchored in the supported WO 2.72 to form single-atom Pd/WO 2.72 owing to the special 4d orbit of Pd and nonstoichiometric 2D planar structure of WO 2.72. Single-atom 5 % Pd/WO 2.72 is prepared in this work, showing excellent bifunctional electrocatalytic behaviors with high E 1/2 of 0.86 V for ORR and low E j= 10 of 1.59 V for OER in alkaline medium, and the ∆E is 0.73 V, which outperforms the Pt/C and RuO 2. Furthermore, the 5 % Pd/WO 2.72 -ZAB has a high open-circuit voltage (OCV) value of 1.491 V, a large power density of 168 mW cm−2, and a large specific capacity of 633 mAh g−1. Besides, the 5 % Pd/WO 2.72 -ZAB also has good cycling stability. [ABSTRACT FROM AUTHOR]