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

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 (NC) 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 NC and carbothermal reduction. Interestingly, WS₂/NC serves the purpose of innovative and robust active sites for ORR through an efficient four-electron transfer process with excellent durability. Remarkably, WS₂/NC 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/NC 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/NC 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/NC such as MoS₂/NC, MoSe₂/NC, and WSe₂/NC.