Nanoengineering of MoS2 Electrocatalysts for Efficient Hydrogen Evolution Reactions
In our recent work, efforts have been made to synergically enhance the conductivity and active-site abundance of MoS2, achieving the high current densities and low onset overpotentials for HER.[4-6] For example, we proposed a new route to confine MoS2 growth within an in-situ formed polysaccharide matrix from glucose condensation during hydrothermal processes, and after the following carbonization, MoS2/C nanocomposites evenly integrating ultrathin MoS2 nanosheets (2 ~ 4 nm) with conducting carbon were successfully harvested (Fig. 1a). The MoS2/C exhibited an excellent HER activity characterized by higher current densities and lower onset overpotentials than the conventional MoS2. In particular, the MoS2/C with a suitable MoS2 content of 14.8% showed a small onset overpotential of ~80 mV, a high current density of 88 mA cm-2 at η = 200 mV, which are ascribed to the abundant rim-sites on ultrathin MoS2 nanosheets and the improved conductivity by carbon. On the other hand, a facile microwave-assisted hydrothermal method was further introduced to fabricated active-site enriched MoS2 nanosheets employing reactant self-shelter, in which the excessive S source (e.g., thiourea) would cover the highly-active Mo-sites during MoS2 formation, and then be removed by following treatment with H2SO4, resulting in abundant active sites on MoS2. The electrocatalytic test well-confirmed the significantly improved active-sites (~3 orders) and conductivity as compared with the traditionally prepared MoS2. Thanks to the facile synthesis and outstanding electrochemical behaviors, our effort is expected to pave the way for earth-abundant, economic and efficient electrocatalysts used in energy conversion and storage.
 A. B. Laursen, S. Kegnaes, S. Dahl, I. Chorkendorff, Energy Environ. Sci., 2012, 5, 5577.
 C. G. Morales-Guio, L. Stern and X. L. Hu, Chem. Soc. Rev., 2014, 43, 6555.
 T. F. Jaramillo, K. P. Jorgensen, J. Bonde, J. H. Nielsen, S. Horch, I. Chorkendorff, Science, 2007 317, 100-102.
 L. C. Yang, S. N. Wang, J. J. Mao, J. W. Deng, Q. S. Gao, Y. Tang, O. G. Schmidt , Adv. Mater., 2013, 25, 1180.
 Q. S. Gao, N. Liu, S. N. Wang, Y. Tang, Nanoscale, 2014, 6, 14106.