Oxygen reduction reaction (ORR) is a key chemical process determining many electrochemical applications of materials, where the requirements on ORR activity may differ strikingly, e.g., accelerated for electrochemical catalysis but inhibited for protective anticorrosion/lubricating coatings.
Our Topic: Using density-functional theory calculations, we have comprehensively studied the electrochemical adsorption behaviors of many important radicals (O2, O, OH, OOH, H2O) on MoS2-based structures (e.g., pristine planar surface, surfaces with point defects, edges) in acid/alkaline solutions, from which their ORR activities (indicated by overpotential) are derived.
Our Results: (1) The ORRs on pristine/defective surfaces always require large overpotentials (> 1.0 V), indicating a defect-immune resistance of planar MoS2 surface against ORR; (2) However, the ORR overpotentials on edge defects can reach as low as 0.66 V, corresponding to a relative high activity close to that of the prototypical catalyst Pt (0.45 V); (3) The decisive thermodynamic and electronic-structure mechanisms underlying such contrasting ORR behaviors of point and edge defects are also revealed in depth.
Our Achievements: This work not only (1) quantitatively explains the performances of MoS2 in both galvanic corrosion and electrochemical catalysis, but also (2) provides a novel & useful Structure--ORR Map that can facilitate adapting the realistic MoS2 to versatile electrochemical applications, e.g., pristine/defective surfaces for ORR inhibition (in protective coatings) and edges for ORR acceleration (in electrocatalysts).
Our Publication: Y. Hao, P.-L. Gong, L.C. Xu, J. Pu, L. Wang, L.-F. Huang, "Contrasting Oxygen Reduction Reactions on Zero- and One-Dimensional Defects of MoS2 for Versatile Applications", ACS Appl. Mater. Interfaces (2019). DOI:10.1021/acsami.9b14502 [URL]