Oxygen vacancy defect tungsten-oxide-quantum-dot-modified nitrogen-doped graphene with interfacial tiny primitives to boost oxygen reduction reaction

Ultrafine quantum-dot-modified nitrogen-doped graphene has attracted board interest and has become frontier research in metal-air batteries and fuel cells. In this study, oxygen vacancy defect tungsten oxide quantum dots (V_o-WO₃ QDs) are embedded in nitrogen-doped graphene (NG) to form abundant heterogeneous interfacial electrocatalysts (V_o-WO₃ QDs/NG), which exhibits advanced electrocatalytic activity for oxygen reduction reaction (ORR) in an alkaline electrolyte. The optimized V_o-WO₃ QDs/NG-5 (W content of 0.14 wt%) exhibits high onset potential (0.932 V vs. RHE) and decent half-wave potential (0.762 V vs. RHE) with high stability, which outperforms other reported tungsten metal oxide-based ORR electrocatalysts. The outstanding electrocatalytic performances of V_o-WO₃ QDs/NG-5 are contributed by higher amount of oxygen vacancy and defects in V_o-WO₃ QDs, as well as tunable interfacial electronic properties between the V_o-WO₃ QDs and NG support. Furthermore, the density functional theory (DFT) is systematically conducted to determine the electronic properties and interface charge transmission for V_o-WO₃ QDs/NG entity, providing important insight on the electrocatalysts in terms of band regulation and electron transport at the active interface between V_o-WO₃ QDs and NG. Our finding paves an efficient pathway to design highly active hetero-structural and durable electrocatalysts for ORR applications based on defect-rich metal oxide QDs supported on nitrogen-doped graphene.