Self-Assembled TMD Nanoparticles on N-Doped Carbon Nanostructures for Oxygen Reduction Reaction and Electrochemical Oxygen Sensing Thereof

Here, we report on a universal carbothermal reduction strategy for the synthesis of well-dispersed WS2 nanoparticles (∼1.7 nm) supported on a N-doped carbon (NxC) nanostructure and the electrocatalytic activity toward oxygen reduction reaction (ORR). Bulk WS2 powder (2 μm) is the source for WS2 nanoparticles, and dicyandiamide is the source for NxC and carbothermal reduction. Interestingly, WS2/NxC serves the purpose of innovative and robust active sites for ORR through an efficient four-electron transfer process with excellent durability. Remarkably, WS2/NxC suppresses the peroxide generation due to the dominating inner-sphere electron transfer mechanism where the direct adsorption of the desolvated O2 molecule on the electroactive centers takes place. The mass activity (at 0.4 and 0.85 V vs RHE) of WS2/NxC outperforms the previously reported transition metal based electrocatalysts. The study further establishes a correlation between the work function and the ORR activity. We have also exploited WS2/NxC for electrochemical oxygen sensing, and there exists a direct correlation between oxygen sensing and ORR as both depend on the oxygen adsorption ability. Finally, the carbothermal reduction strategy has been extended for the synthesis of other TMDs/NxC such as MoS2/NxC, MoSe2/NxC, and WSe2/NxC.