Highly Dispersed Mo2C Nanodots in Carbon Nanocages Derived from Mo-Based Xerogel: Efficient Electrocatalysts for Hydrogen Evolution

The production of hydrogen via electrochemical water splitting has the potential to enable the utilization of hydrogen-powered fuel cells on a large scale. However, to realize this technology, inexpensive, noble metal-free electrocatalysts possessing high performances for the hydrogen evolution reaction (HER) are needed. Mo2C nanoparticles recently receive much attention as alternative noble metal-free electrocatalysts because their electronic structures are akin to that of Pt. However, the synthesis of Mo2C at nanoscale with high catalytic activity for HER remains a great challenge. Moreover, although efforts have been made to prevent their aggregation, the particles coalesce during high temperature carbonization, which is typically used to produce such transition metal carbides. Here, the synthesis of Mo2C nanodots that are well-dispersed within 3D cage-like carbon microparticles using rationally designed Mo-based xerogels, which are prepared via the sol-gel process as precursors, is reported. During their pyrolysis, the xerogels maintain their structures while the Mo species in them transform into well-dispersed Mo2C nanodots in situ. The as-synthesized Mo2C nano- dots exhibit excellent electrocatalytic activity for HER, in both alkaline and acidic media, while remaining largely stable. The work also demonstrates promising synthetic route and procedure to other well-dispersed yet stable nanocatalysts.