Available online 16 March 2022 Keywords: Defect WO3 QDs N-doped graphene Electrocatalyst Interfacial effect ORR

Abstract

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 (Vo-WO3 QDs) are embedded in nitrogen-doped graphene (NG) to form abundant heterogeneous interfacial electrocatalysts (Vo-WO3 QDs/NG), which exhibits advanced electrocatalytic activity for oxygen reduction reaction (ORR) in an alkaline electrolyte. The optimized Vo-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 Vo-WO3 QDs/NG-5 are contributed by higher amount of oxygen vacancy and defects in Vo-WO3 QDs, as well as tunable interfacial electronic properties between the Vo-WO3 QDs and NG support. Furthermore, the density functional theory (DFT) is systematically conducted to determine the electronic properties and interface charge transmission for Vo-WO3 QDs/NG entity, providing important insight on the electrocatalysts in terms of band regulation and electron transport at the active interface between Vo-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. (C) 2022 Elsevier B.V. All rights reserved.