Covalently Functionalized Layered Mos2 Supported Pd Nanoparticles As Highly Active Oxygen Reduction Electrocatalysts

Molybdenum disulfide nanosheets covalently modified with a 1,2-dithiolane derivative were used as a novel substrate for the immobilization of Pd nanoparticles (Pd-NPs) towards the development of a highly efficient hybrid electrocatalyst, namely Pd-NPs/f-MoS2, for the oxygen reduction in an alkaline medium. The newly prepared hybrid material was thoroughly characterized through complementary techniques such as Raman and IR spectroscopy, TGA, HRTEM, STEM/EELS, and EDS. The Pd-NPs/f-MoS(2)nanohybrid exhibited excellent performance towards oxygen electroreduction with a positive onset potential of +0.066 V and a half-wave potential of -0.116 Vvs. Hg/HgO, along with a high current response, which are superior to those of its graphene counterpart and comparable to those of the benchmark Pd/C product. Moreover, Pd-NPs/f-MoS(2)was proved to be remarkably stable as chronoamperometric assays showed minimum activity loss among the tested materials, clearly outperforming the commercial catalyst. The excellent performance of Pd-NPs/f-MoS(2)is attributable to (i) the high affinity of the catalytic Pd(NPs)with the f-MoS(2)substrate, (ii) the absence of any capping agent for the stabilization of Pd(NPs)onto f-MoS2, and more importantly (iii) the preservation of the integrity of the MoS(2)basal plane during the functionalization process. Lastly, the oxygen reduction on Pd-NPs/f-MoS(2)proceeded through the energy efficient four-electron pathway, showing great potential for the use of layered transition metal dichalcogenides in energy conversion applications, comprising fuel cells.