Atomically Engineered WOx/MoOx-Modified Defect-Rich Pd Metallene for Enhanced Alkaline Oxygen Reduction Electrocatalysis

Defect engineering is a key chemical tool to modulate the electronic structure and reactivity of nanostructured catalysts. Here, we report how engineering defects in a palladium metallene nanostructure results in a highly active catalyst for the alkaline oxygen reduction reaction (ORR). A defect-rich WOx and MoOx modified Pd metallene (denoted as D-Pd M) was synthesized by a facile wet-chemical method. Detailed structural analyses reveal the presence of three distinct atomic-scale defects, that is pores, concave surfaces, and surface-anchored individual WOx and MoOx sites. The presence of this combination of defects results in excellent catalytic ORR activity with a half-wave potential of 0.93 V vs. RHE and a mass activity of 1.3 A·mgPd-1 at 0.9 V vs. RHE, outperforming the commercial references Pt/C and Pd/C by factors of 6.5 and 3.9, respectively. The practical usage of the compound is demonstrated by integration into a custom-designed Zn-air battery. At notably low D-Pd M loading (26 μgPd·cm-2), the system achieves a high specific capacity (809 mAh·gZn-1) together with excellent discharge potential stability. In sum, this study provides a blueprint for the targeted introduction of distinct defect sites into metallene ORR catalysts, leading to materials with outstanding performance metrics.