Mesoporous Carbon Nanotablets Coupled with Mo 2 C Nanoparticles: Combining Morphology and Structure to Realize High Activity for Efficient Hydrogen Evolution

Highly Dispersed Mo2 C 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. Mo₂ C 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 Mo₂ C 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 Mo₂ C 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 Mo₂ C nanodots in situ. The as-synthesized Mo₂ C nanodots exhibit excellent electrocatalytic activity for HER, in both alkaline and acidic media, while remaining largely stable. The work also demonstrates a promising synthetic route and procedure to other well-dispersed yet stable nanocatalysts.

Synthesis of Ultrathin and Grid-Structural Carbon Nanosheets Coupled with Mo2 C for Electrocatalytic Hydrogen Production

Molybdenum carbide possessing a Pt-like d-band electronic structure is considered as one of potential candidates of electrocatalysts and it shows intrinsic catalytic property. However, a high carbonizing temperature easily leads to the coalescence of nanoparticles (NPs). Here, we propose a simple sol-gel route to achieve high dispersity of carbide NPs by designing a Mo-involved xerogel. The results show that molybdenum carbide NPs are dispersed and anchored on the nitrogen-doped carbon nanosheets (Mo₂ C@NC). Ultrathin carbon layers resemble graphene and the network structures act as a support of carbide NPs, which can hinder NPs' coalescence effectively. Nanpoparticles cross-coupled on network-structure nanosheets display the grid shapes. Electrochemical studies indicate that Mo₂ C@NC material exhibits outstanding hydrogen evolution performance in alkaline electrolyte.