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 WS 2 nanoparticles (∼1.7 nm) supported on a N-doped carbon (N x C) nanostructure and the electrocatalytic activity toward oxygen reduction reaction (ORR). Bulk WS 2 powder (2 μm) is the source for WS 2 nanoparticles, and dicyandiamide is the source for N x C and carbothermal reduction. Interestingly, WS 2 /N x C serves the purpose of innovative and robust active sites for ORR through an efficient four-electron transfer process with excellent durability. Remarkably, WS 2 /N x C suppresses the peroxide generation due to the dominating inner-sphere electron transfer mechanism where the direct adsorption of the desolvated O 2 molecule on the electroactive centers takes place. The mass activity (at 0.4 and 0.85 V vs RHE) of WS 2 /N x C 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 WS 2 /N x C 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/N x C such as MoS 2 /N x C, MoSe 2 /N x C, and WSe 2 /N x C.